ArchibasePlanet.com allows you to compose your personal block and expose you artworks to the CAD community and potential customers Download Free Stuff Find and download useful 3D stuff: 3D Models, HQ Textures, CAD and 3D Documentation, Manuals and more.
I found 7 sites that have really awesome and 100% free 3D models. Make sure to only search for.obj,.3ds or Cinema files since some models only come in Maya or Max formats.
Also make sure to check the copyright info to make sure you’re good to go on all of these. This is the premiere place to find 3D models. They have a huge paid section, but if you simply type “free” into the search, it will come up with hundreds of awesome free models. This has quite the collection, with a little bit of everything from cars and trees to furniture and interior models. A great resource with tons of characters and cars. This site has amazing vehicles, anything from WWII tanks to modern race cars. A lot of them come in.lwo format which is Lightwave, but they open great in C4D.