Mesh
I've spent a bit of time recently playing around with Mesh (http://www.mesh.com). I really think this is a great idea, and with the SDK I can't wait for some of the creative applications people will be able to build in this environment. I could take social computing to a whole new level simply by making some of the tricky wiring easier to implement successfully.
Although it's still in development, we've removed many of the restrictions on who can get access to Mesh. Visit the site, take a look and let me know what you think. In particular, if you've got a cool idea as to how to use Mesh to help build tools for the User Group community, I'd love to hear from you. I can't say any more just yet, but you may just be glad you did so!