One to one (point to point):
Most of the major free IM software (AIM, Windows Messenger, Skype, Yahoo Messenger, etc.) offer one-to-one webcam video.
- iChat - Very easy to use if both parties have Macs and firewall issues have been resolved. Firewall issues seem to be difficult to resolve. The audio and video conferencing aspects of iChats don't work with a number of the major brand home routers. This can be resolved temporarily by hooking up the computer being used for the video conference directly to the cable or DSL modem. Apple provides a list of compatible routers.
To connect multiple users:
Open source gate keepers: