Mind42 (read mind for two) is a collaborative mind mapping tool.
The beta service enables you to create a mind map for any purpose. Easy editing tools allow for quick changes, and a variety of functions are available for the entire mind map as well as individual nodes on the mind map. Include images and attachments for a specific node, such as a wikipedia article, or a to-do list. Make mind mapping branches for the various items involved in a particular task, and keep track of changes with the revision history. Invite and manage others to collaborate on a mind map with you.
Mind42 is rather helpful, but is limited in the fact that its only current offering is mind mapping. Its collaboration tools are great for teams needing to keep organized, and the revision history means that no information gets lost along the way. The ability to add images and links makes mind42 a dynamic mapping service, and would be a great addition to a web-based document creation tool such as Google Docs or Zoho, or as an add-on feature for team-based services such as egnyte. The inclusion of a whiteboard service such as Yugma or Octopz would be beneficial to mind42 users as well.