This is my list where you can get Social Networks signals like facebook share, likes, g+1 tweets and followers.
Social Signals are a good way to give authority backlinks to your site
These are my favourite exange sites. They have a lot of active users and you can easy get about 100-200 signals per dayCode:youlikehits.com socialmediaexplode.com addmefast.com fblikesyou.com addsocials.com linkcollider.com swapes.com