CADClick

A database for mechanical engineers that offers access to CAD geometries from different suppliers on mechanical engineering.
http://www.cadclick.de/

CADParts

Produces library symbols and footprints for the Cadence CAD software.
http://www.cadpartsusa.com/

Vanguard Software GmbH

Offers partsCAT, an electronic spare parts catalogue software for publishing catalogues on CD-ROM and online.
http://www.vanguard.at/en/

PARTsolutions

A parts library integrated with many CAD systems for direct invocation, as well as with standard data formats.
http://www.partsolutions.de/index.asp?sid=2

Trace Parts

Library of parametric components for 2D/3D CAD assemblies, which can be used with several CAD packages.
http://www.traceparts.com/

CADSymbols

Online 2D/3D parts library for Solidworks, AutoCAD and other software, in formats including ACIS SAT, DXF, DWG, and IGES.
http://www.cadsymbols.com/

Catalog Data Solutions Inc.

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/