Lots of great optical illusions are available at Fun Visual Tricks & Optical Illusions. We'd like to thank Danielle for suggesting this site. This is a commercial website and is not endorsed by BrainU.
Winner of the 2014 Brain Awareness video contest sponsored by the Society for Neuroscience is VisionIllusion, an educational video about vision and illusion produced in Communicating Science Through Visual Media - a joint RISD-Brown course co-taught by Steven Subotnick and John Stein.
This video (just under 4 minutes long) explores the visual system and how adjacent colors influence the way you see an image.