I was recently introduced to Triberr (thanks Diane!). Triberr is a site that is comprised of tribes, as a member of the tribe you can see what the other members are posting on their blogs. You can then choose to automatically share these posts via the social networks that you connect to your account. They can also do the same.
This has the effect of increasing your reach, if I tweet it goes out to 1500 or so of my followers, which is great, but if it's shared in a tribe then that reach can be increased by ten or even a hundred fold.
I'm already part of a blog sharing group on the Indie Book Bargains website (http://www.indie-book-bargains.co.uk/blogs/) where we can tweet each others posts. On Triberr you can tweet and post to Facebook automatically.
There's a wide variety of tribes covering different subjects, of particular interest to me have been the writing and book tribes. I've also started one of my own, called 'The Cult of Me', so if you sign up then feel free to join my tribe as well as check out the others.
It's not a magic bullet, but I've already seen modest increases in my site visitors and of course it increases your presence on Twitter and Facebook.
Check them out at: http://triberr.com