4 links
CADSymbols
cadsymbols.com
Online 2D/3D parts library for Solidworks, AutoCAD and other software, in formats including ACIS SAT, DXF, DWG, and IGES.
Oh Yeah CAD
ohyeahcad.com
A free online parts library that supports AutoCAD, Solidworks, TurboCAD, and SolidEdge native file format.
PARTserver
partserver.com
A parts library integrated with many CAD systems for direct invocation, as well as with standard data formats