I saw this post on David Harris's blog and thought I'd mention a bit more about mind mapping.
What's a mind map? Wikipedia says:
A mind map is a diagram used to represent words, ideas, tasks or other items linked to and arranged radially around a central key word or idea. It is used to generate, visualize, structure and classify ideas, and as an aid in study, organization, problem solving, decision making, and writing.
I like to think of it as software to help you during those "throw it at the wall and see what sticks" sessions. Instead of a cumbersome Microsoft document I find mind mapping allows you to quickly collect and organize information especially during meetings.
Freemind is a free, open-source mind mapping software written in Java. As such it is cross platform so you can easily run it anywhere you can run Java. The Freemind wiki also has a nice list of alternatives.
If you have never tried mind mapping Freemind makes it easy to give it a shot.