Parts, Hardware, and RepRap Vitamin Sources. Now with Documentation links!

Nuts, bolts, etc.
McMaster-Carr --http://www.mcmaster.com
  There are parts lists including McMaster part numbers available for both the SAE and Metric versions.
  There is also a comparison list for the two.
  Various parts http://www.makergear.com

Complete Vitamin kits. 
Thingfarm -- http://thingfarm.org

Additional documentation and E-books.

Guerrilla guide to CNC machining and resin casting by Michal Zalewski  -- This is far more complete an explanation than I could give on the CNC subject.