buddyPhone - 2.02 

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 200) 

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 - 6.5 

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.

Rave 2 - 2.03 

Rave 2 allows you to talk(just like a telephone conversation) to your ICQ Contacts, or to any other person at a fixed IP or domain name address, worldwide. It offers secure encrypted transmissions to guarantee the privacy of your conversations.