Off Page Optimization is the activity that is done on other sites for our site to increase search engine ranking.
Off Page Optimization activities include Directory Submission, Article Submission, Forum Discussion, Blog Posting, Press Release, Blog Commenting and along with this Social Bookmarking (In Digg, Delicious, Reddit, StumbleUpon) and Social Media Promotion (In Facebook, Twitter, LinkedIn).
Off page optimization creates strong back links for our site which not only helps for search engine ranking but also for drive traffic from sites where we have done all these submissions.