Optics & Color
Was forwarded this yesterday -- a striking color optical illusion reposted at the Bad Astronomy blog at Discover magazine. Somewhat shocking demonstration of how the eye and mind process information about color -- great example for teaching ideas of "reality" defined by sensory perception. (Would've been apropos at the Media Ecology conference).
Also good for teaching 1960s abstraction, and not only Op Art -- I just saw a nice Jasper Johns at the Saint Louis University Museum of Art that employed some similar, though not near as intense, optical effects.