Sixgroups, which is based in Hamburg, is offering site-based communities as plugins to existing webpages (there is a six group integrated in this blog). Sixgroups provide all kinds of elements like a shoubox, twitter integration by keywords (above you see all twits that have 'oliverg' in them, for example), forums etc all flows into a "livestream" (no video ... yet ;) )
As with Ning: If you have one "Six Groups ID" you can log into all other SGs and share your contacts. And more: you can even connect a groups of sites you own under one live community.
In "six groups" I specially like the idea that they kind of said good bye to the idea of a web page. Ok, there is sixgroups.com, but the real action in on the overlays (and Widgets) they put in the pages of their customers.
Like Crowdvine "six groups" is ideal for events, and it is even better cause it fullly integrates with the existing website and lets your visitors stay yon your page. And of course you can project the event's livestream on all screens in all session rooms...
And of course events in SixGroups can also show up in FriendFeed ;).
Rumor has it that Stowe was so impressed with 'six groups' when he saw it in May at the next 08 event in Hamburg that he was only to eager to work with them.
Well I got this info early and promised not to blog it till today at 1430 (but I am not at my desk at the moment). So I just can link at the 6G-Blog and hope you'll find more details there.