Skype is the next phenomenon from the people who brought you KaZaA. Just like KaZaA, Skype uses P2P (peer-to-peer) technology to connect you to other users not to share files this time, but to talk and chat with your friends.
Wengo is a single application to talk, chat and share for free with anyone.
Asterisk is a complete PBX in software. It provides all of the features you would expect from a PBX and more. Asterisk does voice over IP in three protocols, and is able to interoperate with almost all standards-based telephony equipment using relatively inexpensive hardware.
Voix Phone is a multiplatform IAX soft phone with an engine derived from Voix Manager, the powerful Asterisk call manager interface, from wich it inherits its stability and robustness.
With Lucious SMS you can send quickly and easily SMS over various gateways.
iSoftPhone is an easy to use VoIP virtual internet phone for Mac OS X using VoIP to provide full compatibility and crystal clear voice quality in an attractively sleek interface.
Finally there is an easy way to create, send and receive SMS with your Mac and forget about that tiny keyboard on your mobile phone.
eyeBeam is a telephony client created to enhance the user’s communications experience in Voice over IP.
FunkeeStory will help you archive and view the messages on your Treo.
SightSpeed is an advanced Audio & Video calling software.