FriendFeed, the aggregation service we've written about several times in the past, has just released a new feature called Rooms. It's basically a mini version of the service, letting you pick which people you want to let join a special FriendFeed information stream.
Users can make rooms public or private, and casually share links amongst each other. It's a little different from the information overflow of the main service. A good use of this would be a work group who shares bookmarks. Each one could share links they're bookmarking on Delicious and keep tabs on the stream of incoming links from other group members at the same time. People who are into micromanaging will love this.
Rooms sit alongside the standard FriendFeed information stream. There's also the choice at the time of sharing to pick where you want items to be shared, either to everyone or just to specific groups. This is best done with the sharing bookmarklet, which lets you choose right there and then.
One thing that's missing (for now) is a directory of public FriendFeed rooms. In its current iteration, you've got to get an invite to join from the creator, or get tipped off about it from someone else. There's no way to search for rooms you'd be interested in, but I'm assuming that's the next step.