I may have posted about this in the past (did a search couldn’t find it).
Anyway, a colleague of mine introduced me to Mindmaps. I’ve been getting more and more into them, and whenever a concept for a game, or hook, or mechanic comes into my head I "map" it out.
I’m using FreeMind, which is well, free and its available under Linux and Windows.
Anyway, while I’m becoming a bit of convert, (I still use UML for more structured engineering, after the concept is flushed out in a map) one feature I thought was lacking was a way to store the maps online, and update/edit in a "WIKI" style format of collaboration.
Well, I’ve found two sites now offering online Mindmapping collaboration services (Mindomo, and Mindmeister) so I’m trialing them at the moment.