I am not sure if you are very familiar with these ones, but I have been investing some time into Sportstalksocial, Dlike, and Tasteem. My favorite of them is probably Dlike. When I first found it, it seemed kind of spammy. They are working on a way to only post to your blog if you choose to. I think they have a model that has them right on the edge of making it big. With a couple more feature additions I think it will see some really mass adoption.