Cool stuff at NextFest: part II: AR on a PDA
A group from the Vienna University of Technology did some nice Augmented reality stuff using a Dell Axim pocket PC with a tiny little video camera. They had a layout of toy train tracks and when you looked through the PDA you could see a train superimposed on the tracks. You could also control the switches with the pen as could another person who had the second PDA. If you didn't switch properly two of the trains would crash -> they always crashed for me.
Surrounding the tracks were big black and white tokens (the standard ones from the ARToolkit). The developers said that they needed to be big because the resolution of the little camera was so low, and they needed a lot so that you would always have three in the field of view (although it seems to me that you should be able to work off of one). It worked pretty well, if you moved too fast there were problems though.
I could imagine using this in the cosmology gallery for a video version of our audio tours - "virtual" scientists would pop up in the exhibits and tell you about them.