Converting metric to standard and back probably would be good to have.
Found this. There are thousands out there
http://www.breaktru.com/qikconv.html <-- This one is free to download.
http://standards.nasa.gov/history_metric.pdf <-- "A Brief History of Measurement Systems" hahaha BRIEF!
http://www.worldwidemetric.com/metcal.htm <-- this ones web based conversion. looks nice.