I'm addicted to mind-mapping applications. Since I found FreeMind I've developed an obsession for capturing software concepts over software, not whiteboards.
Here's a cool WPF application that maps minds: Cayra. Great layout and graphics capabilities. Incredible user experience.
Don't forget to keep saving your work, I've been experiencing some crashes. But it payees off, the usage is just incredible. What I really miss is importing FreeMind documents.