Process Ace Software
Palm engineering software and Palm hardware for Process and Mechanical Engineers. Steam tables, turbine, heater and pump calculations, handhelds
http://www.processacesoftware.com

Wire Gauge calculations
Java script based online AWG calculations.
http://www.mogami.com/e/cad/wire-gauge.html

FeynCalc
The FeynCalc home page, entry point to information about FeynCalc and related programs for High Energy Physics
http://www.feyncalc.org/

Fermat
Computer algebra system that does arithmetic of arbitrarily long integers and fractions, symbolic calculations, graphics, and other numerical calculations. Free download. Documentation.
http://www.bway.net/~lewis/

Chemical and Plant Engineering Calculations
Here are key calculations for equipment sizing and rating for the chemical process industry from a fellow engineer for compressor, distillation column, exchanger, pump, line hydrualic ratings etc.
http://tierling.home.texas.net/default.htm

Tanker Cargo Calculations
Crude Oil Product Tanker Cargo Calculations, hydrostatic calculation, Calculation Add-in
http://www.cargocal.com/

Satellite Calculations
Includes all types of satellite uplink/downlink calculations, including link budget and angle.
http://www.satellite-calculations.com/

Calculations for equipment sizing and rating for the chemical process industry.
Here are key calculations for equipment sizing and rating for the chemical process industry from a fellow engineer for compressor, distillation column, exchanger, pump, line hydrualic ratings etc.
http://tierling.home.texas.net/

Math Connect
Calculation, metric conversion and more.
http://www.mathconnect.com

MySQL Date Calculations
Learn how to make calculations with dates and times in MySQL Queries.
http://mysql-tips.blogspot.com/2005/04/mysql-date-calculations.html