I discovered MyThoughts for Mac more recently than some of the others listed here, and therefore haven't had quite as much time with it. That said, so far I'm quite happy with it. Of course, it's Mac only. For $49 it's got a pretty good feature set, and as a native Mac OS X application, it performs nicely.

If you use a Mac, and are looking for a MindMapping tool, MyThoughts for Mac is worth checking out... there's a free demo, available here.