A source for design professionals, engineers, and architects to download component drawings from leading manufacturers, in a variety of industry-standard formats. http://www.cadregister.com/
A source for poly-faceted 3D Models of human figures, cars, trucks and construction machinery for SolidWorks, Unigraphics, SolidEdge, and IronCad. http://www.human-ergo.com/
Online 2D/3D parts library hosting, integrated with PTC Wildfire and the ability to do Parametric searches. Formats include PRT, DXF, IGES, DWG. http://www.catalogds.com/