Mind-mapping with Free Mind. It's a brainstorming tool. It's an organizer. Create a mindmap to collect family information, organize your week, or brainstorm a plot thread. I've been using this little program for four or five years. With the latest upgrade it's significantly improved.
Here's an example of one I made in the early stages of RCP to brainstorm the crime, clues, suspects, and motives of characters. You can also store links and customize nodes.
A world of information will fit in a small space by collapsing the nodes and expanding as needed. It's so easy to use, so versatile and it's free!
I've see some intricately designed mindmaps and simple ones like the one at Moving to Freedom for a very simple and creative application of the program. (Preview below.)
For Mac or PC download it here.