Graveman is just a great program! Excellent alternative to K3b if you don't want to load whole KDE, and if you want a nice GTK2 GUI.
Among all Free Software CD/DVD burners, this is the one with the best GUI metaphor. It's like iPod, you look at the user interface and you're like "dude, it just makes 100% sense." From this perspective, it's even better than K3B.
An open, cross-platform journaling program.
A scientific plotting package.