MindMeister - collaborative web-based mind mapping
Thanks to a tip from a reader and his gracious offer of an invite (thanks Robbie!), I've discovered MindMeister, a web-based mind mapping tool that does three things I consider to be absolutely essential for an online offering in this category. First, it is compatible with MindManager, the application I use on both my PCs and my Mac. Second, it allows maps to be shared with others in either read-only or full collaboration mode. Third, it integrates Skype so that IM or VoIP chat can be conducted while collaboratively editing a map.