Portals

MatWeb — Material propery data

Octopart — Search engine for electronic parts

TraceParts — A huge choice of 2D & 3D CAD files, models and drawings.

https://www.tracepartsonline.net — Trace Parts Online — Free 2D & 3D CAD files, models and drawings of mechanical, electrical & mechatronics part catalogs

TSF Global Fastenting Solutions — (Spain)

Zycon — Industrial directory, engineering resource, and vertical search engine