Although I've been using Keynote to keep track of my thoughts and information, I've still been a little disappointed with it. Worse, it seems that development has all but stopped, so it may never get better. On top of that, the Keynote files aren't the easiest format to follow.
Something referenced FreeMind, an free open-source Java mind mapping program, so I decided to try it. It takes a little getting used to, especially since everything is displayed in the map window (it doesn't store text notes which are opened in a separate pane). Actually, that's the only thing I'd like to see (besides maybe a speed increase, which I guess is due to it being a Java application). Anyway, the good things about it are that the files are formatted in XML, the program is super-portable since it's Java, it exports to a nice HTML outline (you can also use an Applet to display it online as a map), and the map format is easy to navigate.
Since I haven't decided on one program or the other, right now I'm updating both everytime I want to add something new, which is pretty annoying, so I'll be choosing one or the other soon...