Autodesk: Point A product support
Cadalog: CAD shareware, parts libraries and much more
CAD fx: CAD plug-ins
Cimlogic: CAD plug-ins
CTAC: Developers of Parafast parametric fastener and hardware components for Mechanical Desktop software
Trilogy Design: Parts & Vendor$: Parts list and BOM software for product designers, engineers and prototypers
MCADCafe.com: Resource for MCAD professionals