Chris Harrison (a PhD student at CMU) is working on a new input method.  Scratching.

Yes, 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).

Scratch Input and Low-Cost Multi-spectral material sensor


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.