Google today announced Google Waves, a new social collaboration, email, twitter, something or other. :) The webmonkey article has a decent description of it though.
As the new user is leaving a comment, everyone involved in the wave can see the comments being typed in, in real time, letter by letter. Edits can be made concurrently, so two or more users can see one anothers’ changes flowing in, even as they’re leaving their comments, making edits or uploading images.
It'll be interesting to see how this does or where it competes when it comes out, that's for sure! Hit wave.google.com for a video and signup page.