The data for this STL is taken from a micro-CT scan of a mouse skull, processed in ImageJ - http://rsb.info.nih.gov/ij/ . The original data was provided by Mark Henkelman of the Mouse Imaging Centre (MICe) http://www.mouseimaging.ca
Files include the whole skull, and then a left half-skull sliced just to the left of the midline. I made this one as I was interested in the structure of the turbinate bones in the nasal passages, and it can be tricky to visualize complex 3D structures like this on a computer screen, even with 3D rendering.
Note that this is downsampled from the original micro-CT image as ImageJ was not able to cope with converting the full file to an STL on my computer. I will also try to upload the 160 Mb 3D TIFF file containing the full scan. The internal detail visible in this file is amazing (sequential images scan from the tip of the nose through the back of the head).
Photos show the half skull printed on a Stratasys FDM machine (black) and an Objet 24 (white). The FDM print is scaled up by an additional factor of two due to resolution limitations.
UPDATE 2012.10.15: Uploaded a demo print of the model done on the Zcorp ZPrinter 450 (same size as the black ABS one). The colour is arbitrary, I put it in to test the printer's colour capabilities.
UPDATE 2013.04.06: Uploaded a demo print of the model done on the Replicator2 (red, same size as the black ABS one). Quality on surfaces where I had to remove support / raft is only marginally inferior (if anything) to the Stratasys machine using soluble support, surfaces that did not require support are equivalent.