If you are a game designer, be sure to bookmark this handy Reddit thread (if you haven’t already). Looks like it is frequently updated & focuses on free assets that don’t require sign-up to download.
Want to get started with 3D modeling? Check out Seamless3d, a NURBS based general purpose 3D animator & modeler. It’s designed to be easy to use (ages 4 & up). Free for download & open source under the MIT License.