Mathematica
I was introduced to Mathematica around 2007. Ever since, I have been a faithful fan. Mathematica frees the users from manipulating equations and formulas and thus frees their minds to understand the underlying theory. For the various examples within the site, I have provided the Mathematica code that a student can use to solve the same example. In addition, the interactive tools are implemented using webMathematica which allows me to use the Mathematica code to produce interactive web examples. If you are interested in the webMathematica code, you can request it by sending me a message.