These are live apps that update in your browser. They cover a variety of distribution applications. Some are designed mainly to be instructional. Others, like most of the protection apps, are useful for real enginnering.
Right now, many of these are beta quality. Use caution! No warranty! These apps work best with a recent version of Firefox or Chrome. Most of them will work with version 11 of Internet Explorer, albeit with a few quirks; only a few of the apps work with Internet Explorer 9 or earlier versions. Most apps should work on modern tablets and phones.
To report on bugs, suggest features, or propose additional calculators, please file an issue here or email me.