Bubbl is one of several mindmapping applications available online. I've been looking for something I can use with my web design students. I want them to map out some fairly large sites and I need something that lets them do this easily and collaboratively.
I'm going to try out a few other programs but we'll be using Bubbl in the meantime. I'm thinking of maybe using just a wiki of some sort. I'm in a class that will be exploring some of the uses of wiki's this semester and maybe that will give me some guidance on the "perfect" program.