MakerBot’s Thingiverse is a thriving design community for discovering, making, and sharing 3D printable things.
License: Creative Commons (Various)
The NIH 3D Print Exchange provides models in formats that are readily compatible with 3D printers, and offers a unique set of tools create and share 3D-printable models related to biomedical science.
License: Creative Commons (Various)
Here you’ll find a growing collection of 3D models, textures, and images from inside NASA. All of these resources are free to download and use.
License: Public Domain
Scan the World is an ambitious initiative whose mission is to archive objects of cultural significance using 3D scanning technologies, producing an extensive platform of content suitable for 3D printing.
The Smithsonian is begining to share high quality 3D scans from its collection as printable STL files and virtual 3D tours.