You should check out Carline Leaf's stuff. She did a lot of animated films with sand on glass and paint on glass. Very cool stuff. See http://www.awn.com/leaf/
ragtag are any of the animations on the site? because i couldn't fine any.
Also I once ran across a video of an artist who used charcoal to make animations that were pretty cool. Anyone know who that is?
It's a while since those films were made, so I'm not sure if they're available for download anywhere. I think they are still available for sale though, they were all made at and published by The National Film Board of Canada. http://www.nfb.ca/e/index.html They did lots of very cool experimental animation there, with everything from wooden cubes, to sand, to whatever. You should check them out.
Caroline Leaf really is amazing. Her sand and paint-on-glass films zoom in and out, shift "camera angles" as if flying, dissolve between scenes, all by shifting the material on the glass stage. They're well worth seeing.