I love optical illusions. Here’s one called the Raar Effect.
It consists of several circles with detailed color and shape patterns. Wherever you happen to be looking on the image, the circles around it seem to spin slightly. If you stare at one place for a few seconds, the spinning gradually slows to a stop. If you keep moving your eyes around, then the circles seem to be spinning all over the place.
When I first went to the site, I thought it was a Flash file. It’s really very mesmerizing. Check it out.
Your post inspired me to make this desktop picture for my PowerBook:
http://richd.com/pictures/raar-effect-tibook.jpg
It’s a bit outta control, but I thought you might enjoy it.