voice over IP, internet telephony, etc+

• see https://ostel.co/ and https://jitsi.org/

• http://skype.com

• PBX software for linux http://www.asterisk.org/ (and bsd/osx/etc .. http://www.voip-info.org/wiki-Asterisk+introduction )
• gnomemeeting / voxilla / etc+: NetMeeting? compatible
• gspeakfreely http://gspeakfreely.auriga.wearlab.de/
• speak freely for unix-likes http://www.fourmilab.ch/speakfree/unix/
• gphone » http://gphone.sourceforge.net/
• kphone
• what about rat? (When speakfreely is used in rtp mode, it can communicate with gphone and rat.)
• commercial, cross platform (wintel/mac) http://www.xten.com/
• linphone » http://www.linphone.org/?lang=us&rubrique=1

• http://voip.ring.org/
• Creative Labs USB VOIP Blaster on NetBSD?, Linux, and Windows

• http://www.openh323.org/
• linux voip notes http://www.bewley.net/linux/voip/

• ichatAV seems to work well.
• XMeeting aims to make a video conferencing platform http://xmeeting.sourceforge.net/
• …so does the earthlink conference manager http://www.research.earthlink.net/confmgr/