Loren Heniy links to a couple of interesting demos for those interested in multi-touch. Both feature some adventures in physics. The first is a video featuring Crayon Physyics. The second is a series of photos located here. The third shows yet another video on how to create your own multi-touch box.
Also of note, apparently Google is supporting some multi-touch efforts through student summer programs. Interesting.
This article may contain affiliate links. Click here for more details.