ibiblio
Ibiblio: How Many? A Dictionary of Units of Measurement
The Center for Mathematics and Science Education at the University of North Carolina at Chapel Hill provides an interesting and easy-to-use dictionary of the history and meaning of many measurement terms. Metric, International, and...
Other
All math.com: Us/metric Conversion Tables
Convert metric measurements to U.S. Measurements and the reverse, too. Easy to follow tables have sections for area, length, mass,temperature and volume.