Fabulous game ...
and a really nice implementation with a very challenging AI. Pity that it's practically abandoned... the binaries are usable if one installs an old version of libstdc++ and fudges things a bit, but I've not managed to build from source at all. There is no configure script, and I've not managed to work out from the C++ error messages what the project's true dependencies are (it probably includes a specific C++ std.lib. version :-/ )
An open, cross-platform journaling program.
A scientific plotting package.