On the State of Scientific Telecollaboration?

Douglas Arnold asks: "This summer I will take over as director of the Institute for Mathematics and its Applications in Minneapolis, one of the world's premier institutes in the mathematical sciences. (This year's program on mathematics in multimedia should interest many Slashdot readers) The IMA hosts visits by over a thousand scientists a year, mostly using Linux to meet their computing needs. I am interested in pursuing telecollaboration and teleconferencing at the institute, so a scientist there can work with a scientist off-site, carrying on a mathematical discussion as if they were at the same blackboard. What sort of hardware and software exists for this sort of application? Is there anything that works well under Linux? I am thinking of things like shared whiteboards, 'collaboratories,' networked graphics tablets (on which it is comfortable to enter formulas and do calculations), integration with audio or video conferencing systems, and so forth."