Brain Facts from the Society for Neuroscience (an introductory pamphlet on the study of the brain)
An excellent anatomy web site from the University of Washington.
Viperlib (the VISual PERception LIBrary) - an excellent collection of illusions and other demonstrations of how your visual system works.
Mighty Optical Illusions Some illusions, and many interesting photos mis-labeled as illusions.
(Note! Brain Voyager has a great *FREE* teaching resource called "Brain Tutor". Click the "Downloads" menu at the top of the BV page and select "Brain Tutor for OS X [or PC]")
MRI Physics Intro from Oxford.