Via boingboing, I just ran across The Stereoscopic Skin Clinic . I was expecting to see stereo-pair photos, but the presentation on that page is interesting - the photos are presented as animated GIFs, which alternate quickly between each of the photos in the stereo pair.

For most of the photos, this is enough to trick my brain into seeing a 3D, rotating, figure.

It's just a little bizarre, but very cool.