When it comes to taking notes, a simple text editor may do for some. However, Linux offers a wide range of specialized programs for this task, some of them shipping advanced features and powerful formatting and organizing tools.
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.