Type of Site:
Science, Art, Optical Illusions
Michael Bach's Optical Illusion page not only showcases some of the best illusions on the web; it explains how and why they work. The site is wonderfully interactive and often gives buttons that help the user control their experience. There are even hints to help with especially tricky visuals. This is an excellent resource for optical illusions.
Not all optical illusions can be seen by all people and kids in particular may struggle with some of them. Also, the descriptions of how the illusions work are technical in nature. Don't expect children to understand, or even care, what's going on. Sometimes the magic is enough.