Mind maps are great. Nothing like a colourful grid to plot ones thoughts. I am familiar with
bubbl.us I used it last year for study - and it helped me get my head around some concepts that were new to me. When I went to log in I was amazed that I remembered my user name and password - I have generated so many online accounts, I need a mind map to keep track of them. Below is said mind-map:

I was in search of a different type of map, so was happy to use this opportunity to explore. I tried
mindmeister, and in an effort to multitask, I learned how to use it, and plan my daughters 16th birthday party at the same time. Here is the result:

I was impressed with the online demonstration for mindmeister - courtesy of
demogirl.com, that's am interesting how-to site I'll go back to for other demos.
Update: Since initially writing this post, Andrew has drawn my attention to
XMind which is an open source mind mapping tool that can be downloaded onto your computer. Its an alternative where your maps are created and stored on your computer, rather than their website. It kind of feels old-fashioned!