Social SEO isn't mentioned here. Here are a few starters. Tumblr and Reddit will give you Do follow links. You can get these through many forms Blogs, pictures, just sharing links. Stumbled upon the same. Do follow links. My personal favorite is posting a picture to tumblr tweeting it from there and sharing it to my FB fan page from there also. So it can reach out to most of my followers. They will retweet, retumbl, and share my post all giving me exposure plus the much needed high PR Backlinks from tumblr.