NASA's model collection is mostly contains models of their satellites however it also contains some of things like space suites, shuttles, and a martian crater. Unfortunately, most of these models are not printable. NASA has conveniently separated the printable models on this page.
The Smithsonian museum has also started uploading 3D models of items from their collection to their Smithonian X3D website. Though many of these models look amazing many also look unprintable so be warned before you try to print them.
- HHMI Biointeractives (small, but hopefully growing)
-Abe (entering 8th grade)