A nice family tree program and the only one for Linux I've found that does top-down (ancestor at the top of the page, as opposed to on the left) tree charts. This is how my family's tree was originally done by a professional genealogist, so its good to be able to keep with that format as the additions come in. Its also nice to be able to adjust the font of the chart to fit it on a smaller number of pages. No HTML charts, but I use ged2html for that. Recently updated to works well at 800x600. Provided as a Fedora RPM but installs out-the-box on Mandriva 2006.
An open, cross-platform journaling program.
A scientific plotting package.