Google's exclusive little club just got a little less exclusive. As promised, the search giant's shiny new social network Google+ has opened up, giving users the ability to invite friends via email. (If it's not working on your system yet, trying logging out and then logging back in.) Existing users, it's time to start building out those Circles to avoid the sort of accidental social networking shenanigans Google is working so hard to curb. Everyone else, we're sure you'll be getting one in your Gmail inbox soon enough. In the meantime, how about prepping yourself by reading