Spotter is software that can check students' answers to symbolic and numerical problems in math and science. It recognizes an answer regardless of the form it's in, and the instructor can put in helpful hints as responses to frequently-occurring mistakes. Symbolic answers can be input in a notation closely resembling normal human math notation (e.g., xy rather than x*y, and sin x instead of sin(x)). Spotter runs as a Perl CGI application on a Web server; the student doesn't need to install any software.
When is an extremely simple personal calendar program, aimed at the Unix geek who wants something minimalistic. It can keep track of things you need to do on particular dates. It's a very short and simple program, so you can easily tinker with it yourself. It doesn't depend on any libraries, so it's easy to install. You should be able to install it on any system where Perl is available, even if you don't have privileges for installing libraries. Its file format is a simple text file, which you can edit in your favorite editor.
FooTex is software for converting LaTeX math markup into MathML, HTML, or PNG. It is basically just a wrapper for texvc and blahtex. It provides some extra functionality, and gives a consistent interface to the functionality of the two underlying packages. The documentation is built into the source code. When you install footex, the documentation will be installed as a man page.
Loveitloveitloveit! Unison has been one of my crucial tools for years now. The recent versions are extremely solid.
I've played around some more with the new java version and want to correct some inaccuracies in my earlier comment and also add some more information. The controls for changing the scales do work, but only when data collection is not active. (The C++ version allowed it to be done on the fly.) There are no numerical labels or grid-lines on the graphs like there were on the C++ version, but you can hover the mouse to read off coordinates. The performance issues referred to in my earlier comment may just be because the moving average window is turned on all the time; however, there does not seem to be any way (as there was in the C++ version) to turn it off, so the effect is that performance is poor. Sound input sometimes inexplicably fails to work on my machine. The Stop button takes about 5 seconds to respond on my system, which is particularly unfortunate since you can't adjust the scales without stopping.