DIAX


This is a full featured and very small IAX based software phone for Microsoft Windows platforms (only). The application is distributed as a freeware for personal use. Click here to see the online help for a complete description of the application. Some of the main features are:

registering with Asterisk PBX;
supporting IAX2 protocol (only);
can act as a remote PSTN/GSM/PCS/CDMA gateway for any Asterisk server;
multiple audio codecs support (with auto-negotiation): aLaw, uLaw, GSM, iLBC, Speex;
can register with multiple servers (max. 8);
independent audio codec configuration for each registration server;
fully support for the ATCOM AU-100 USB phone (http://www.atcom.com.cn/engweb/bUSBPhone.html);
fully support for the Yealink  USB phone (http://shop.voismart.it/products.php?cat=12);
fully support for the Eutectics Inc. USB phones (http://www.eutecticsinc.com/products/products.html);
web browser integration (start app and/or dial using a link like diax://number/alias);
configurable audio latency;

E-Phone


EPhone appears to be a Windows based SIP softphone.

Ekiga


Ekiga (formerly called GnomeMeeting) is a VoIP and video conferencing application for GNOME and Windows. It is distributed as free software under the terms of the GNU General Public License. It is the default VOIP client in Ubuntu. Ekiga supports both the SIP and H.323 (based on OpenH323) protocols and is fully interoperable with any other SIP compliant application and with Microsoft NetMeeting. It supports many high-quality audio and video codecs.

Ekiga was initially written by Damien Sandras in order to graduate from the Université catholique de Louvain. It is currently developed by a community-based team led by Sandras. The logo was designed based on his concept by Andreas Kwiatkowski.

Empathy


Empathy is an instant messaging client which supports text, voice, video, file transfers, and inter-application communication over many different protocols.
Empathy also provides a collection of re-usable Graphical User Interface widgets for developing instant messaging clients for the GNOME desktop. It is written as extension to the Telepathy framework, for connecting to different instant messaging networks with a unified user interface.

Empathy has been included in the GNOME desktop since version 2.24.[1]

Firefly


Editor's note: this used to be the softphone for IAX but wasn't available for Mac. They've now released a beta version for Mac, which I'm downloading as I type this.

Small program: fast to download and uses very little system resources
Intuitive user-friendly menu
Instant messaging and free calls to other Freshtel users
Free Voice Mail system

FlaPhone


Flaphone? is a SIP (Session Initiation Protocol) compatible web softphone, that is working in web browser without installation of any specific software*. Everything that you need is internet connection, speakers and microphone**. Flaphone? users can call each other, to SIP phones, and any phone numbers, if SIP provider accounts are configured in control panel.

* You need Adobe Flash Player version 9 or higher to use flaphone.
** If you use flaphone? without a headset, your conversation partner will hear his own echo.
This is caused by Adobe Flash Player, that doesn?t have echo cancellation feature yet.

IAX Telefon


This Softphone is based on IaxClientOcx I designed from iaxclient library. This softphone is just for giving credits to the IAX/libiaxclient creators and designers. Very easy to use with most of the options any professional dialer can have. Designed in VB. multi language support, skin base interface

PC-to-Phone, PC-to-PC call models supported
Easy to install and configure
Professional and Stylish Look n feel
NAT/Firewall support
Automatic Gain Control, and noice filters
Audio Tunning Wizard for setting sound/mic device and volume/Playback.
Can be used on Windows 98, Millennium, NT4, 2000, XP and XP+ Operating Systems
Multiple Codecs support, iLBC,Speex,GSM,ulaw,alaw
Audio Filters, Noise,Echo,CN,AGC,AAGC support
Very compact in size
Local signalization (Dial tone, busy, ring back, etc.) will be added soon.

Jabbin


Jabbin is an Open Source instant messaging program that allows free PC to PC calls using the VoIP system over the Jabber network. The new Release 2.0 use the libjingle protocol.

JackenIAX


Want to be able to make phone calls around the world from anywhere? Answer your home phone from a hotel in Tokyo? Well, you can with JackenIAX and an Asterisk server or using an VoIP provider that supports the IAX2 protocol. JackenIAX supports multiple lines, and to switch between calls, all you have to do is double click. If you want to try it out without signing up for an VoIP account, just get a free FWD account.

JIAX


JIAX is a web based softphone which is written in Java.

KCall


KCall is the telephony application of Kontact. It supports computer telephony integration and at the same time integration into KDE's infrastructure. KCall does this by using KDE's addressbook, which in turn can be a server-based groupware addressbook.

KIAX


Kiax is a softphone (soft phone, VoIP client) with a simple and comfortable user interface for making VoIP calls to Asterisk PBX. It depends on the iaxclient library to use Asterisk's IAX2 protocol for easy call configuration and audio setup.

KPhone


KPhone is a SIP User Agent for Linux. It implements the functionallity of a VoIP Softphone but is not restricted to this. Licensed under the GNU General Public License, KPhone is free software. KPhone is written in C++ and uses Qt.

LinPhone


Linphone is a VoIP application for Linux operating system (although it is reported to work also on FreeBSD and OpenBSD). Windows XP is fully supported [1]. It uses the Session Initiation Protocol for communication and is licensed under the GNU General Public License. Linphone uses GTK+ for GUI and on Linux it can be also run as a console-mode application. Of course, even though Linphone is a software tool, in order to use it, you?ll need some basic hardware, such as a headset and a microphone. And if you want to use Linphone as a complete phone system you?ll need an account with a VoIP provider.

MiniPax


Minipax is newest generation of Vidosystem Softphone. Our engineer had successfully recode sip engine to produce more robust, small application, better nat traversal sip softphone.

Minipax NOW support SIP tunneling. SIP tunneling works where clients firewall blocked or on a country where voip is blocked. SIP tunneling also give more security to voip

Minipax support hold function, mute function, mic/spk volume control, transfer call, forward call, call recording, auto login to web billing CDR, call history, address book, balance display, fully skinable look n feel, available for private label and logo.

MiniSIP


Minisip is a SIP User Agent ("Internet telephone").

It can be used to make phone calls, instant message and videocalls to your buddies connected to the same SIP network.

The source code is available as a number of libraries under the GNU Lesser General Public License (LGPL) and applications under the GNU General Public Licence (GPL).

MizuPhone


Mizu SoftPhone is our award winner professional VOIP client application based on the open standard SIP protocol with an easy to use modern interface. With Mizu SoftPhone you can connect to any SIP server on the public internet or on your local area network.

Multiple accounts and multiple SIP server registrations combined with a powerful dial plan can minimize your telecom bills while using the  greatest features from the VOIP industry.

Features include IM, presence, HD Video, history with voice records, skype like voice quality using ultra-wideband codecs and much more. 

A free edition is also available based on the same engine as our corporate sip softphone but it has some features disabled (like G.729 and wideband codecs,  multiple accounts and file transfer over SIP)

MozillaVoIP


MozillaVoIP is a built in softphone for Thunderbird and Firefox.

Firefox details:
All VoIP functionality is built in the extension, there is no need to install any other software
Video support
One-click call feature to dial a phone number directly from the web page you are browsing
Can be used with any SIP provider
VoIP accounts can be provided by Abbeyphone
Available languages are English and Italian

Thunderbird details:
Call your contacts from the Thunderbird addressbook.
Send SMS to your contacts.
One-click call feature to dial any number directly from the mail you are reading.
Available languages are English and Italian.

Mumble


Mumble is a free, open-source, cross-platform voice over IP application. Its primary users are gamers, and it is similar to programs such as TeamSpeak and Ventrilo. It uses a client-server architecture where users who want to talk connect to the same server.

Mumble's stated design goal is not to create the most elite gaming utility but to create the most social one. The goal is to recreate the feel and social interaction of a LAN party. As such, Mumble has a very simple administrative interface and most of the engineering effort is put into sound quality and low latency.

As of version 1.1, all communication is encrypted to ensure user privacy. As of version 1.1.7 Mumble has native support for Logitech G15 keyboard LCD display.

NimBuzz


Nimbuzz for PC/Mac lets you call, chat and interact with your friends on all popular instant messaging and social networks.

Connect to all your friends at once

Chat and interact with all your friends from one place: Windows Live Messenger (MSN), Yahoo, ICQ, AIM, Google Talk, Facebook, MySpace, and more. One secure login for all communities! Mobile version also available.

OfficeSIP


OfficeSIP Messenger provides enterprises with advanced instant communications for free. Compatible with Office Communications Server 2007, OfficeSIP Messenger delivers reliable performance combined with trouble-free deployment and management. Supporting text, voice and video chats, the free softphone implements ICE, STUN, and TURN protocols to easily traverse NAT and firewalls, and supports TLS for ultimate communication security.

OfficeSIP Messenger is based on industry-standard libraries used by Microsoft Office Communicator, providing robust, reliable operation in business environment. Thanks to the high-quality code, OfficeSIP Messenger ensures the highest level of compatibility with audio clients and Web cameras, and provides landline-quality calling for both voice and video.

PhonerLite


PhonerLite is a clearly arranged application for Windows. PhonerLite enables your PC to use it for internet telephony (VoIP , Voice over IP ). Pre-conditions are a full-duplex sound card , a microphone and speakers (alternativelya headset), an  internet connection and a registration at a provider supporting the protocol SIP .PhonerLite supports several SIP profiles, each configurable independently. In thesame way the integrated phone book and call log are easy to use.

QuteCom


QuteCom (previously called WengoPhone) is a free software SIP compliant VoIP client developed by the QuteCom (previously OpenWengo) community under the GNU General Public License (GPL). It allows users to speak to other users of SIP compliant VoIP software at no cost. It also allows users to call landlines, cellphones, send SMS and make video calls. None of these functionalities are tied to a particular provider allowing users to choose among any SIP provider.

SFLPhone


SFLphone is a SIP/IAX2 compatible softphone for Linux. The SFLphone project's goal is to create a robust enterprise-class desktop phone. While it can serve home users very well, it is designed with a hundred-calls-a-day receptionist in mind.

SFLphone is a free software and is distributed under the GNU General Public License version 3. It is developed by Savoir-Faire Linux, a Canadian Linux consulting company, in partnership with the global community. Savoir-Faire Linux provides to users easy-to-install packages for most of the main Linux distributions.

SightSpeed AKA Logitech Vid


What Vid lets you do
Have you ever wanted to see someone, even when they were far away? Vid makes it easy using your webcam and Internet connection. You see and hear them. They see and hear you.

You can skip the screen names, the hassles, and the complicated settings and get right to smiling face

SJphone


SJphone® is a VOIP softphone that allows you to speak with any other softphone running on a PC/PDA, any stand-alone IP-phone, or using Internet Telephony Service Provider (ITSP) with any traditional wired or mobile phone. It supports SIP and is fully inter-operable with most major VOIP vendors and ITSPs.

SIP Communicator


SIP Communicator is a Java VoIP audio/video Internet phone and instant messenger that supports some of the most popular instant messaging and telephony protocols such as SIP, Jabber, AIM/ICQ, MSN, Yahoo! Messenger, Bonjour, IRC, RSS and counting.

SIP Communicator is completely Open Source / Free Software, and is freely available under the terms of the GNU Lesser General Public License.

Team Speak


TeamSpeak is proprietary Voice over IP software that allows users to speak on a chat channel with other users, much like a telephone conference call. A TeamSpeak user will often wear a headset with an integrated microphone. Users use the TeamSpeak client software to connect to a TeamSpeak server of their choice, from there they can join chat channels.

Telephone


Editor's choice for Mac

Telephone is a VoIP program which allows you to make phone calls over the internet. It can be used to call regular phones via any appropriate SIP provider. If your office or home phone works via SIP, you can use that phone number on your Mac anywhere you have decent internet connection.

Telephone is really easy to use. It's for the Mac only.
Universal binary, Leopard.
Languages: English, German, Russian.

TPad


Acts as a 2nd telephone line for your house for Free (no monthly costs or line rental).
Simple, easy to use - just like making a telephone call but using your PC and up to 60% cheaper than your phone.
Make Unlimited Free VoIP Calls to other Tpad Users anywhere in the World (PC to PC).
Make Ultra Low Cost Calls to any landline / mobile in the World.
Crystal Clear Call Quality - (sound like you are in the same room as your friend) - plus many, many more benefits...

Twinkle


Twinkle is a softphone for your voice over IP and instant messaging communcations using the SIP protocol. You can use it for direct IP phone to IP phone communication or in a network using a SIP proxy to route your calls and messages.

Twinkle version 1.4.2 is now available for download.
Twinkle is available for Linux only (GPL license).

VBuzzer


Powerful VoIP and Internet Fax Software
Instant Messaging
Multi Protocol IM MSN, Yahoo, AIM, ICQ
VoIP Pc to Phone Calling
Internet Fax
File Transfer
Multi Language Chat Translation

Ventrilo


Ventrilo uses a Client / Server architecture.

At the present time the client is supported on the following platforms:
Microsoft Windows 9x / NT / 2000 / XP
Macintosh PowerPC OSX 10.3 or higher.

At the present time the server is supported on the following platforms:
Microsoft Windows 9x / NT / 2000 / XP
Linux i386
FreeBSD i386
NetBSD i386
Solaris Sparc 64bit
Solaris i386
Mac OSX PowerPC 32bit

The server is designed so that multiple copies can be started on the same computer and properly supports multi-homed systems, even including interface filtering.

In the Windows environment the server can be started manually or configured to run as an NT Service when using one of the Microsoft NT/2000/XP Operating Systems. The NT service can also be configured to start multiple instances of the server program and has built in features to automatically restart servers if the administrator issues a shutdown command or if a program bug is encountered.

In the UNIX environments the server can be started manually or configured to run as a background daemon. Multiple instances of the UNIX server can be started on the same computer. It's also possible to configure them on a "reserved" basis in which they are started automatically at certain times and then terminated later.

Voix Phone


Voix Phone Is a multiplatform IAX soft phone, its engine derives from Voix Manager, the powerful Asterisk call manager interface, from which it inherits stability and robustness.

Voix Phone has been thought with simplicity in mind, all feature needed by the user, fast and easy usable, with the minimum configurations, just fill the phone login information and play.

We hope that this our contribution could be useful to who requires of a simple but advanced soft phone, Voix Phone is distributed freeware for non commercial use.

WXCommunicator


wxCommunicator is a cross platform open source SIP softphone enabling users to make multiple calls, use several accounts, chat and create conferences. It is very configurable and should work with any VoIP provider. It is based on customized sipXtapi client library and wxWidgets 2.8.x GUI library and distributed under GNU GPL version 2 licence.

X-Lite


CounterPath's X-Lite is the market's leading free SIP based softphone available for download. Combining voice and video calls, Instant Messaging and presence management in an intuitive and familiar interface, X-Lite helps you seamlessly transition from a traditional hard phone environment into the world of Voice over IP.

If you are already a VoIP or Broadband service subscriber (i.e. you receive VoIP service from your local Service Provider or local IP-PBX), X-Lite 3.0 lets you make audio calls to any softphone, mobile or landline number, and make video calls and send IMs to any softphone which supports these functions.

Whether you are are having a simple voice conversation, enjoying a video conference call or engaging with friends over IM, X-Lite leads you down the new path of personalized communications.

YakaPhone


YakaPhone was developed by Bits Valley Ltd. along it's line of YakaSoftware products for use with its telephony service, YakaCall (http://www.yakacall.com). You can, however, use it for FREE with any suitable telephony provider you wish. It is Open Source and may be modified but any pre or post modification commercial usage requires prior authorization. See License Agreement for further details.

ZFone


Zfone is a new secure VoIP phone software product which lets you make secure encrypted phone calls over the Internet. It lets you whisper in someone's ear from a thousand miles away.

Zfone enables you to have a private conversation any time you want with anyone, anywhere ? without buying a plane ticket.

The ZRTP protocol used by Zfone will soon be integrated into many standalone secure VoIP clients, but today we have a software product that lets you turn your existing VoIP client into a secure phone. The current Zfone software runs in the Internet protocol stack on any Windows XP, Vista, Mac OS X, or Linux PC, and intercepts and filters all the VoIP packets as they go in and out of the machine, and secures the call on the fly. You can use a variety of different software VoIP clients to make a VoIP call. The Zfone software detects when the call starts, and initiates a cryptographic key agreement between the two parties, and then proceeds to encrypt and decrypt the voice packets on the fly. It has its own little separate GUI, telling the user if the call is secure. It's as if Zfone were a "bump on the wire", sitting between the VoIP client and the Internet. Think of it as a software bump-on-the-wire, or a bump in the protocol stack.

Zoiper


A key-feature for the Zoiper Communicator is that you can choose to use it simultaneously with the Zoiper Service and with your VoIP service provider. Doing so will save you costs and will ensure your continuous communication.

Please note that you can decide not to use the Zoiper Service with your Zoiper Communicator by simply choosing "I do not want to use this service" from the Zoiper Communicator interface upon initial startup, or by just not logging-in to the service on startup.

The Zoiper Service is embedded in your Zoiper Communicator and assures FREE advanced Zoiper-to-Zoiper communication.

You can easily configure your SIP and IAX accounts with your existing VoIP provider in your Zoiper Communicator.