I have a lot of tools for planning, but Freeplane is probably my baseline, goto tool for sketching my thoughts. I love its branching web, the ability to format, drag n' drop reorganization, linking: It has more abilities than I can fully list here with any due credit. You can auto-number nodes, list attributes for a node, add notes, icons, pictures, links to other maps or files (I have a link to a spread sheet on this one as well as links to other maps). I highly recommend this for sketching and more. I'll just post a link to the Wiki. It has a link to the Freeplane site. http://en.wikipedia.org/wiki/Freeplane
I'll also add that the maps can be imported to Scrivener. The file format is freemind's, which Scrivener decided to support, so Freeplane can be imported as well.
I use a similar application on my iPad called iThoughts. Scrivener will import the file and turn it into a Binder outline. Does this application import similarly into Scrivener?
Yes. It creates an outline based on the map, so "Races" would be an entry and I believe (can't recall as I've only done it once) that each racial name would create an entry under "Races". It does this without wiping anything in the binder, which is nice.