Kaltura.com does a dozen things right in one place; unusual for a modern creator/social-networking site, they focus heavily on creation. Most unusually, they do all of this with video, the black sheep of the collaborative family : small clips, visualized; smooth remix process, with interface on the client and reasonably response time on the server without redrawing a whole screen; the best memes of history and authorship transparency realized with large-font rounded-corners elegance.
Now who is using it ? where are the transclusions for mediawiki instances? I can’t wait to see the beta site develop.