Your site needs an FAQ.
No, really. It does. Although you personally might think that the activity feeds and groups and profile editing links are in the most obvious locations in the world, your users will not. They’re used to their own oft-frequented social networks (cough, Facebook), and they’ll ask you why clicking on their avatar doesn’t automatically bring them to a “change your profile picture” page or if logging into your site using Facebook Connect will mean that everything they post will automatically get cross-posted to their Facebook wall. In addition, users want to know about your site features.