I used to love using the Mindmapping osftware on my old work PC, but couldn't justify the expense when I went solo. Freemind though does the job perfectly, even down to the icons to add on the nodes. It lets you export as an HTML list, which is good to get the bullet points into OPenOffice if you're using it to outline a document or article.
It also has a file mode to let you browse your hard disc as though it were a mindmap,. Apparently you can write filters to create different modes, they are working on a scheme mode, I suppose you could have an XML or AIMLmode, even a PERL mode, who knows. Seeing as I also love the Brain software, would be good to find a way to combine the two.- maybe a mode might get somewhere close.