Shapefest - A massive library of 3D shapes for everything!
Wannathis - 3d illustrations and freebies
PixCap - A browser-based 3D animation editor and assets library.
Craftwork - A collection of User Interface resources made by Craftwork
Iconscout - Design Resource Marketplace.
Sketchfab - Sketchfab is an industrial design software tool is useful for ideation and for beginners in the industrial design field.