XMind is an Eclipse-based mind mapper (brainstorming) tool. I've found it to be quite adequate for brain dumps.
I still like Microsoft Word's outlining tool. It's one of the few reasons to still use Word.
But XMind provides a nice way to create and visualize "bubbles" or groups of ideas.
There are some videos which show how to use it. Each of these are about 1-2 minutes and a good way to try before you "buy".