Stock Material and Parts:
McMaster Carr
Hunnington Vacuum products
Boston Gear
Swagelok Fittings
Fastenal Fastners
Microgroup tubing and fittings

Calculators:
Darex calculational tool for machinists
Engineers Edge Web Page

Material Data:
Mat Web: Material Propertry Data
Anything you want to know about copper and copper alloys
Mechanical Properties of Common Plastics

Standards:
ANSI Standards
Tap Drill Chart

Autodesk Inventor:
Autodesk Home Page
Inventor 3D Parts - Downloadable
Inventor 3D Parts and Totorials - Downloadable