Mind maps are a great tool for capturing brainstorming ideas. I dont intend to talk at great length here about how mind maps work as there are numerous articles on the net about mind maps and a good starting point is Wikipedia.

The interesting part for me was seeing these maps at work capturing user story requirements, which I have been doing for a few months now to great effect.
A couple of weeks ago I was talking through with Richard Banks (of Readify) about this process and it sparked his interest. So off Richard went and ran a number of sessions using this approach, again with great results.

Richard (ever the blogger) has gone to the trouble to write up his findings in this great blog post. Have a read through it and see some of his HUGE mind maps hes put online. Credit to Richard (again) for another good blog post, it reminds me I really do need to write more articles, more often :)

My personal choice for mind mapping software is NovaMind. As you can imagine there are a raft of mind mapping tools available, some of which can be used online in a collaborative manner.
e.g. mindomo