buddyPhone - 1.55 

buddyPhone lets you directly voice chat over the Internet by directly connecting via IP address to others using buddyPhone. Also provides full ICQ integration which allows you to directly connect to another user through ICQ. Small and easy to use, buddyPhone is a good voice chat program for those who talk to specific people.

Internet Phone - 5.01 Beta (build 171) 

Excellent two way real-time voice chat in Half & Full Duplex with users list to choose. Internet Phone features caller ID, call waiting, muting, blocking and directory assistance. Also offers automatic voice activation and supports audio conferencing.

MediaRing Talk - 5.9 

PC to PC internet telephone which can make and receive calls 24 hours a day. You don't even need to be logged on! Features include Automatic signaling and connection to the internet. Short lag time and an excellent connection. Caller and Receiver must both have software installed.

Net2Phone - 9.51 

A new technology which makes it possible to place domestic and international calls from a personal computer to any telephone in the world. You must have an account with them to use this, and they charge per minute for connections. The charge is typically less then a normal phone call.

Web Phone - 4.02e 

A new IRC program in the tradition of Internet Phone, with a different, phone console-type interface.