Google have just launched Poly, a giant repository of mostly free 3D models, aimed at AR and VR content creation. The site is available at https://poly.google.com/ with most models downloadable in OBJ format, a file format compatible with the vast majority of 3D applications including Max, Maya and Blender. This service is very similar to Microsoft’s Remix3D, launched along side the Windows 10 Creator Update. The majority of models in Poly are licensed under the CC-BY open source license, a very game developer friendly license simply requiring attribution.
You can see Poly in action (and a bit of Remix3D) in this video.