Interesting stuff, Kelly. It's fun to see what other people use on a daily basis.
AWS Standard Weld Symbols (24" x 36" chart on the wall)
AISI Thickness Tolerance Ranges (for sheetmetal)
Ryerson Stocklist Handbook (this is a great source of info regarding metals ranging from sheetmetal to tubing, steels and alloys)
Vendor Tool List (this is an itemized list of tooling for our vendors turret punches. It is very helpful when designing a part to know what tooling is available for punching various holes and slots.)