Video Thing has a cool experiment in shooting panoramic video using a Christmas tree ball mounted on a boom in front of a DV cam. An After Effects plugin turns the resulting reflection into a cylindrical environment video. Very cool.
I did some experiments a while ago using this setup, only with still images instead of video. My old Kodak 210+ wouldn't focus close enough to get a good image of the ball, so I turned out this:
The code was pretty simple to write: just convert from reflected rayspace into a cylindrical map. Cool stuff.