MindMeister, a web-based mindmapping application, is now out of beta and looks pretty useful. The basic version is free, although you are limited to 6 mindmaps. The premium version is $4.16/month (paid yearly) and includes unlimited maps, removal of advertising, exporting to Freemind and Mindmanager file formats, along with the ability to embed mindmaps in blogs/other websites. Every new user gets one month’s free access to the premium features.
With Skype integration and a really nice, clean Web 2.0 layout, this could be a winner!