1)   sharpVoice(tm) Client 6.0
sharpVoice is a internet telephony program that enables free PC-to-PC and inexpensive PC-to-Telephone voice conference calls even with slow internet connections.

 2)   PeerMe 0.9.6
PeerMe has developed an instant messaging platform which supports Peer to Peer Voice, PC to PC and PC to handheld voice communications, instant messaging, and peer-to-peer file transfer all over public Internet connections.

 3)   IPi Phone 0.3
IPi Phone is internet IP to IP telephone software that allows you to talk and use text chat. IPi Phone is easy to use. All you need to know is the other person IP address and you can connect to them and start talking over the internet for free.