Gliffy is a new web-based app for creating sharable diagrams. It's very nicely done. Even as a personal mindmapping tool, it's far superior to anything else out there (Mayomi, for instance), but the addition of near real-time collaboration puts Gliffy in a league of its own. You can quickly map out ideas and tasks and invite others to work with you. And as you'd expect from a Flash (OpenLaszlo) application, it's ultra-responsive and uber-slick. You can save diagrams to Gliffy, export as a jpeg or SVG file or instantly publish to a blog, wiki or webpage. What's more, Gliffy maintains a revision history, allowing you to return to previous versions of your work.
No word yet on when they'll release a public version, but I think Gliffy will go down well. As for the biz model, they'll be releasing paid versions in the near future.