If you stare at the little black cross in the center of this ring of blinking purple dots, the dots will turn green and eventually disappear. But if you stare at the purple dots themselves, you'll see that they only blink off momentarily and are never green. Remarkable. Link (via Random Good Stuff)
Reader comment: David says: Here's a page with 57 optical illusions and visual phenomena. The purple dot illusion is also on there, but figured other fellow BB readers would be longing for more."