There's a program developed at Cornell (for Macs at the moment, but a PC
version is promised) called "CU-SeeMe" which permits videoconferencing
using ordinary computers and videocameras.  The digitizing software costs
about $300, according to an article in the Cornell Alumni News, and is
already included in most new macs.
 
At home-modem speeds, one gets about a frame every 5-10 seconds: the
faster links between campus mainframes can get up to near-tv 10 frames per
second.  I should think one image per 5-10 seconds would be fine for
transmitting graphics and the like ... I don't think it has audio, so far,
since the article mentions that one can scroll typed text across the
bottom of the video window.  Several video windows can be open, each in a
different location (Philadelphia, California, and the Syracuse office of
NYSERNet are mentioned as current sites) ... all it takes is that the
computer be 'on' and the camera running.
 
--bayla