Brain Pictures: A set slices from an NMR brain scan, displayed using Javascript so that the user can view them in series by moving the mouse pointer. Non-scientific.
Comparative Mammalian Brain Collections: Univ. of Wisconsin site has images showing the brain's internal architecture of specimens from over 100 mammalian species for studying differences in brain function and evolution.
Flybrain: An online atlas and database of the Drosophila nervous system.
The Whole Brain Atlas: Excellent MRI views of the normal and diseased human brain. Collaboration of MIT and Harvard Univ.
UCLA Laboratory of NeuroImaging: Research on brain mapping, structure and function, and related imaging technologies.