http://www.thoughtex.net/This is far from easy to use but I was surprised by what this application turned out to be.
Overall, it's worth a peek for any developer out there.
I know nothing about development but even if you set aside that it's a mindmapper, I've never seen an application with a feel quite like this. This includes other .Net apps.
I wouldn't bother with the feature list though.
This feels more like what Adobe Air apps should feel like but more powerful and the static screenshots don't quite represent that.