Cisco telepresence is some seriously cool stuff. Well, they kicked it up a notch recently by demonstrating on-stage telepresence. I'll link to the video - but it essentially reminds me of R2D2 beaming princess lea to deliver a message. :)
John Chambers was in Bangalore, India and brought on stage with him (virtually) Martin De Beer and Chuck Stucki, from San Jose. The demo apparently uses a presentation system from Musion, who does 3D holographic projection.
Check out the video here