CU-SeeMe is a desktop videoconferencing program for PC's and Macintoshes.
A commercial version of CU-SeeMe is available from White Pine Software.
A freeware version is also available from White Pine Software, or from
Cornell University under copyright of Cornell and its collaborators.  

CU-SeeMe provides a one-to-one conference, or by use of a reflector, a 
one-to-many, a several-to-several, or a several-to-many conference 
depending on user needs and hardware capabilities.  CU-SeeMe provides
audio and video conferencing on both the PC and the Mac platforms.

CU-SeeMe is intended to provide useful conferencing at minimal cost.
Receiving requires only a personal computer with a screen capable of 
displaying 16 grays and a connection to the Internet.  Sending requires 
the same plus a camera and digitizer (see specs below) which can cost as 
little as $100 to add on.
