[daltore]

Forgot to mention a couple of command-line things:

-Timidity++ - MIDI sequencer with some of the best voices I've heard.
-Rhythmbox - iTunes replacement for Linux.
-apropos - Type in a keyword and it'll give you every program, library, or general topic having to do with it
-aptitude - Linux package manager, fast, automatic, no dependency hell.
-motion - Connect any webcam and this program will detect a moving picture and interpret it.
-occrad - Optical character recognition program, the computer-based version of what we have on this year's controller
-wget - Command-line file download program, takes the headache out of writing programs based on server files

All of these are on Linux, sorry, but I think a few of them have Windows ports, and you can force them into Apple/Darwin if you're determined enough.