UX Week '08 had two great talks that you must see if you are serious about multitouch and NUI.
The first is by Darren David and Nathan Moody of Stimulant. Currently, they are acting as "out-sourced brains" on the Microsoft Surface Team. I met them when I was there and was very impressed by the quality of their thinking and execution.
Darren David & Nathan Moody | UX Week 2008 | Adaptive Path from Adaptive Path on Vimeo.
The second video is by Dennis Wixon, the Usability Research Director on Surface. He gives an incredible talk about the Surface vision. I first heard this spiel from August De Los Reyes and was asked to give a keynote reflecting on these ideas myself, so I don't know where the core content came from originally...but it's insanely inspirational thinking.
Dennis Wixon | UX Week 2008 | Adaptive Path from Adaptive Path on Vimeo.