Second Life is an option to consider.
Funny, because I just built the University of Epic Proportions in SL.
But as others mentioned, I don't think it reaches a wide enough audience, because to use it at all, you need broadband, and to use it effectively, you need a hell of a good rig, headphones, mic, and some practice in SL.
I would like to see stuff like that done IN SL, but not use SL as the primary platform.