Excellent online brainstorming tool

I am totally digging this. It's a Flash-based, in-browser mindmapping tool. It is fast, simple, good-looking, easy to use, and -- this is more important than I used to think -- fun to work with. All the shapes and colors make me more creative. I've been working on a redesign of one of my courses, and part of the process has been trying to organize the content of the course visually as it currently stands. This service has made it really easy. I love it. Thanks bubbl.us!

Embedded mindmap:


Partial screenshot (click to enlarge):