Epicenter - Wired Blogs: "The Flash-based player, included with Uber's drag-and-drop assets management system, launches with an exclusive music track by hip hop subversive Gnarls Barkley. Uber CEO Scott Sassa told Underwire, 'We think that shared media is a vital part of the community and something that Facebook hadn't pursued on its own. What we're providing is an opportunity to very quickly access tons of media, so you immediately grab any kind of media, easily store it and easily share it.'"
Just taking a quick look around Uber, it appears to be a pretty standard social network with a slight bias towards photography. Their most notable differentiator is the ajax-y pages where you can drag assets off of other peoples pages to drop into your library.
I'm guessing there is more (I only spent about 2 minutes on their site), check it out for yourself...
UPDATE: I missed the forest for the trees... the big announcement was the debut of Facebook's open platform and positioning as the "anti-MySpace". Totally open to any/all widget makers. There is good coverage of the ones announced at Mashable: http://mashable.com/2007/05/24/facebook-platform-30-apps/.