Google Poly seems like a nice UI for searching for 3D models. It's a bit annoying because you have to change the search options to remixable to find ones you can download. Models seem to all be OBJ files.
Seems to compare favourably in user experience to other options (blender-models requires facebook likes to download, Yobi3D has several steps to find download links on other websites). But selection is probably worse (best content seems to be provided by Google).
