Edistorm looks like an interesting tool for collaborative brainstorming. Group brainstorming sticky note boards (storms) can be set up with a background template, e.g. 5 up, SWOT, venn diagrams, etc. You place colored sticky notes with text, organize however you want, you can add +1 votes using a voting system, and add comments to notes. There's some kind of recomendations feature that will suggest new topics, which I guess might only work well with certain content types.
You can export a report that shows the stickies added and their votes and comments in a nicely laid out PDF or as an Excel doc. You can also export the laid out sticky note workspace as a PDF graphic. An iPhone app gives you mobile access to your storms.
Pretty sweet. Looks like public storms are free for now. I'm liking it.