Gather
Gather is a site that offers a large number of ways to interact with one another as well as find information important to you. You can tag websites, share links to articles, share images, read "essential" articles on given subjects, and join groups that discuss specific topics. You can get a free membership in order to leave comments and start your own groups, but you can also subscribe to groups using RSS feeds which lets you read all of their shared articles. The site is nicely laid out and the breadth of choices before you is amazing. Definitely worth checking out.