BasKet This is one of my favorite KDE applications. BasKet is called by some a kill application for Linux, due to its completeness regarding features and a different approach compared to other notes applications.
I use Tomboy, an open source notetaking app, to cull and organize the hundreds of bits of information I track, and to prioritize it on to-do lists on the fly. When we first reviewed Tomboy 0.3.5, it had some obvious flaws. The project has had a number of updates since then, and the newest version, 0.10.0, really makes the grade.