Reference

• Online Conversion - Units conversion
• Metal Reference - Drill, tap and taper sizes
• Screw Sizes - Screw sizes (note links to larger sizes at bottom of page)
• SolidWorks - The 3D design program with which I'm most familiar
• Shop Reference - from MIT
• Weld Symbols - a helpful explanation
• Material Densities - a sampling of material densities.

Inspiration/Discussion/Misc.

• core77 - A great design magazine website and discussion board.
• DesignScienceToys - Fun toys
• London Design Museum
• David C. Roy - Kinetic sculpture
• Arthur Ganson - More kinetic sculpture
• AskTog - A very intelligent page on all sorts of design
• Jakob Nielsen - Another great page on different kinds of design and usability issues
• Donald Norman - Yet another design "expert" on the web