An omnidirectional projector with a camera inside watches your hand movements and reacts fast, like a planetarium-wide Surface table. Does it give you a Zaphod-sized ego? Hell yes it does. Check out this vid:
As you can, see from the photo above, the computer is tracking hand gestures using a basic gesture language: pinching to grab, pulling hands apart to zoom, moving hands together to pan and rotate. In this demo, the content spewed from the omnidirectional projector is the WorldWide Telescope (the thing that made Scoble or somebody cry). It's pretty cool, especially when you see him pan all the way back to reveal the Big Bang, and then zoom in again to see that glowing dot that turns out to be the flippin' Milky Way.
And yes, it does remind me of the Total Perspective Vortex from Hitchhiker's Guide, even if it's not powered by a single piece of cake. (Trust me, I looked.)
Microsoft's TechFest is an annual jamboree of innovation and gadgetry from Microsoft Research, which means that while none of it is coming out as is in products in the near future, it's essentially what product development people use to add cool stuff to their actual releases. I'll be here all day.