Use a Wiimote to Make a Low-Cost Multi-touch Whiteboard
This is THE coolest DIY wii remote hack/mod ever. Johnny Lee from Carnegie Mellon describes how to make a digital whiteboard with a wii remote and projector. (Added bonus; it's multi-touch)
Software for this hack can be found here :
http://www.cs.cmu.edu/~johnny/projects/wii/
Guess what I want to make after winter break. Yeah, a Wii whiteboard. Awesome.