This thread is a place to share links to sites which provide 3D content under a creative commons license, if you wish to post a link, feel free to do so, just be sure to point out which license it is released uner:
http://resources.blogscopia.com/category/models/
Plenty of modern interior furniture, bathrooms, kitchens, loungerooms. its all quite high poly, but with a bit of decimation should be usable in game. All under CC by 2.5 or 3
http://www.esi.uclm.es/museo/index_en.html
A good collection of computers and consoles, all under CC by 2.5, again, quite high poly, but they react well to decimation.
http://e2-productions.com/repository/modules/PDdownloads/
The official Belnder repository, a fair sized collection of blender models, the licensing is strange, they say totally free in one place and then copyright in another, still looks to be cc by 0
This list has a great number of awesome sources
http://www.gamedev.net/topic/544073-free-2d3d-art-assets-09/
Just a quick note regarding CC licenses below 3.0... Unfortunately, due to certain requirements, they're not allowed in under the Debian Free Software guidelines, and you can't just convert the CC 2.x content to CC 3.0. If you want to upload anything that's released under a CC license below 3.0, you have to contact the author first and get them to update the license.
Bart
Nasa has a page of its 3D models that are not copyrighten unless otherwise marked
http://www.nasa.gov/multimedia/3d_resources/models.html
ShareCG has a whole searchable section marked "unrestricted use" In the license section it says free for any use whatsoever, which I'd guess means public domain
http://www.sharecg.com/b/5/3D-Models/?keywords=Enter+keywords&member_typ...
Every single asset from the mmo Ryzom has been released under CC by SA 3.0
http://media.ryzom.com/
Updated links:
Blender 3D Model Repository: http://www.blender-models.com
Ryzom assets: http://atys.wiki.ryzom.com/wiki/Category:Ryzom_assets
Everything on BlendSwap has a CC license.
https://www.blendswap.com/blends/categories
I recently published my own CC0 collection! Feel free to check it out.
https://www.3dmodelscc0.com/
I'll be uploading some of my content on opengameart as well! As the URL suggests, everything is licensed as CC0.