Great Free Tool for Brain Dumps

My father recently told me about a really neat tool called FreeMind. I've been working with it now for a few months and I love it. There are actually a number of so called "mind mapping" software tools available, some commercial, others free. Microsoft Visio also has a Mind Mapping tool called a "Brainstorming Diagram" (under "Brainstorming"). I've found Freemind very useful when attempting to put nebulous ideas or plans to paper. It's a great "first-pass" tool for just getting things out of your head.