The "How Far Is It?" service uses data from the U.S. Census and a supplementary list of cities around the world to find the latitude and longitude of two places, and then calculates the distance between them (as the crow flies). It also provides a map showing the two places, using the Xerox PARC Map Server.Martindale's Reference Desk: Calculators On-Line Center
This site provides very extensive set of Java script based online calculators that cover many subjects.MegaConverter
MegaConverter.com is an ever-growing set of weights, measures, and unit conversion/calculation modules covering both ancient and modern units of measurement.