Fluid Flow: This is a javascript program which will simulate a pipe network. Pressures can be specified at the nodes and then flow rates are iteratively calculated through the specified pipes. It also calculate unknown pressures from known pressures or flows by making use of PID controllers.

Unit Converter: This is a javascript program which will convert a wide range of physical units. Unlike most unit converts, mine parses through a text string and is able to add units (e.g. 3*in+5*m) and divide units (e.g. 3*kg/m/s^2 = 3*Pa).

Excel Unit Converter: This is an excel worksheet with imbedded VBA code which will convert between a wide range of units. Unlike most unit converts, mine parses through a text string and is able to add units (e.g. 3*in+5*m) and divide units (e.g. 3*kg/m/s^2 = 3*Pa). It is also extensible, so it is possible to define additional units. Best of all, its free and open source. I would appreciate links pack to this page however.

Chemical Property Calculator: Another javascript program which will has a range of chemical preprty data (sorry I don't have the source for any of it). Using this data it can calculate vapor pressure, viscosity, thermal conductivity, enthalpy, and binary diffusion coefficients.

Equation of State Tool: This is a work in progress. A javascript program allows thermodynamic flash calculations to be performed on mixtures made up a variety of common chemicals. The program uses the Peng Robinson with Stryjek and Vera modification (PRSV) equation of state to determine the compostions of the liquid and vapor phase and the Lee Kesler enthalpy/entropy calculations (these are based off of the Benedict-Webb-Rubin equation of state).