Free Unit Converter
   Conversions of area, density, energy, force, length, mass, power, pressure, speed, temperature, volume and bytes.
   http://www.flowmeterdirectory.com/flowmeter_unit_converter/index.htm

KW Liquid tank Heating calculator
   To determine kW required to raise the temperature of various liquids.
   http://www.thermalinc.com/math/roundtank.htm

Martindale's 'The Reference Desk: Calculators On-Line'
   A very extensive set of Java script based online calculators covering many subjects.
   http://www.martindalecenter.com/Calculators.html