Via Digg- Here’s a great optical illusion, it kinda makes me dizzy after a bit though. And here’s another site which also has a lot of other ones, equally dizzying. None of these are animated GIFs, they work by simulated nonlinear luminance adaptation and simulated contrast adaptation- more about that here. I think I’ll try to make a wall sized one. If I could make one large enough I bet a crowd could potentially cause free-throwers to miss at a basketball game (slate had an article on one attempt like this).