3D Printing

Rep Rap (influential open source project)

Blog, filament spools, and a few other items (Oregon)

Steven Devijver writing on building a printer (http://reprapbook.appspot.com/)

Tech Paladin parts (Cupertino)

Inventables "The hardware store for designers" (USA)

Terawatt Industries (parts and printers) (Boulder, CO)

Robot Digg (parts) (China)

Primer on stepper motors

"Taxonomy of Z axis artifacts in extrusion-based 3d printing"

Ada Fruit is, well, Ada Fruit. I can't explain.

Thingiverse, source of a vast library of 3D models