The SX 70/Time Zero film will give you 3" x 3" photo with some brilliant color. You can also manipulate the image for about 2 hours after the shot. The earlier you work with the emulsion, the more drastic the effect...later (say 10-12 minutes) the effect can be as subtle as an impressionist painting. I have a couple of these in my personal gallery.
The 4x5 film is great also. Type 79 gives you great color at a higher speed, but for the most part, it is the end result in itself. Type 59 is another animal. The speed is slower (65-80 ISO), but once the shot is taken, you can either transfer the image (peel apart the film early and press the chemistry onto watercolor paper) or actually lift the emulsion off an place it on paper, wood, etc. In this case you are actually boiling and lifting off the image from the backing.
Polaroid has a good CD that is free for these techniques. Have fun with it.