Facebook has a new app called "Rooms."
http://www.rooms.me/Supposedly it requires no actual Facebook account. On paper this seems like if you got a lot of buy-in from your friends, this could replace a lot of other things like forums, delicious, pinterest, group.me/beluga, etc.
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The downside is that the functionality is restricted to iOS.
It seems a bit like Google+ Communities?
https://itunes.apple.com/us/app/rooms-create-something-together/id924643029