Womp - 3D Made Easy
Shapefest - A massive library of 3D shapes for everything!
365+ 3D Printing Objects - A year's worth of monetizable 3D printing things.
Wannathis - 3d illustrations and freebies
AstroPrint - Slice, Store, and Print your 3D files from any web enabled device.
Craftwork - A collection of User Interface resources made by Craftwork