I'm a heavy mind map user - in my experience you either don't use them at all, or you use them all the time.
If you fall into the latter camp, there are quite a few mind map tools on the market. What a lot of people don't know, myself included until last week, is that you can create them with Visio. The advantage I've found is that this enables you to have technical architecture diagrams plus mindmaps all in the same Visio file, it can be a great time saver and keeps all project documentation in one place.
http://www.microsoft.com/education/analyticalvisio.mspx has a short tutorial on how to do this - it uses Office 2003. I'm using Office 2007 and the functionality is the same plus has improvements.