Chris Harrison (a PhD student at CMU) is working on a new input method. Scratching.
Johnny Chung Lee (from the Wii remote fame) posted an article with some videos. The technique looks rather interesting. You can scratch and tap on a surface, and use it to control your computer, PDA, etc.
The full article is here (including a video of the scratch method).
Here is another user interface. It uses a space and time method to keep track of what you were doing. The video explains it better than I can.