Online calculators with variety of engineering functions, including unit conversion, periodic table, piping applications, and electrical applications.

http://www.monachos.gr/eng/calculators/calculators.htm
A calculator that takes calculations out to many, many digits

http://www.home52365.fsnet.co.uk/bcalc.htm
Programs for analytical applications. Includes technical support.

http://www.aasdt.com/statistics/mlr.html
An RPN calculator applet and supporting Java library.

http://www.hpl.hp.com/personal/Hans_Boehm/crcalc/CRCalc.html
A interactive computer math system that uses standard JavaScript as the scripting language, and a collection of re-usable math oriented components such as a complete MathML DOM implementation, and a MathML viewing / editing control.

http://numerator.sourceforge.net
An online graphing calculator Java applet.

http://humblestar.net/GCalc
Multi-function shareware calculator, and unit conversion utility for Windows. Four modes of operation: statistics, trigonomety, base-n, and unit conversion.

http://www.rjsoftware.com/FNA/
Explains commonly used words specialized to this field. Includes examples and some graph illustrations.

http://www.dpi.state.wi.us/dpi/standards/mathglos.html