BrainMaps.org is totally cool. 50 TB of images of the brains of 12 different animals (so far). You can zoom in to see microscopic structures with a resolution of just under 0.5μm per pixel. One of their recent papers in NeuroImage describes the technique they used to acquire and assemble the images. Pretty cool stuff.
BrainMaps.org is an interactive zoomable high-resolution digital brain atlas and virtual microscope that is based on over 15 million megapixels of scanned images of serial sections of both primate and non-primate brains and that is integrated with a high-speed database for querying and retrieving data about brain structure and function over the internet. Currently featured are complete brain atlas datasets for various species, including Macaca mulatta, Chlorocebus aethiops, Felis catus, Mus musculus, Rattus norvegicus, and Tyto alba.