The Evolution of Time Measurement http://physics.nist.gov/GenInt/Time/time.html
Aztec Calendar http://www.azteccalendar.com
Dave's Math Tables: Weights and Measures http://www.sisweb.com/math/general/measures.htm
World Wide Metric Conversion Calculator http://www.worldwidemetric.com/metcal.htm
A Dictionary of Measures, Units and Conversions www.ex.ac.uk/cimt/dictunit/dictunit.htm
Your Weight on Other Worlds http://www.exploratorium.edu/ronh/weight
Simple Machines http://library.thinkquest.org/J002079F/sub3.htm
The Franklin Institute Online Simple Machines http://sln.fi.edu/qa97/spotlight3/spotlight3.html
