I find mind maps useful for many purposes. The process of clearing your screen, fullscreening your mind mapping tool, and immersing yourself in a topic of interested is a great brainstorming exercise.
Today, my goal wasn't creativity, it was to build a map of main components of Rails 3. You'll likely find the PDF more useful as its nodes are clickable and refer back to the Rails API (and github in a couple cases where I found documentation to be more useful).
This isn't a comprehensive map. Let me know what I've missed.
(This map was created with MindNode Pro, an easy to use, cheap, and high quality OS X app, proving that sometimes you can have your cake and eat it :-)