This social sharing internet tool allows you to enter any URL and gives you a count of how many times it was ever shared across the 4 major social sharing sites: Facebook, Twitter, Google Plus and LinkedIn.
List of Social Bookmarking Sites
Diigo - Web Highlighter and Sticky Notes, Online Bookmarking and Annotation, Personal Learning Network. Diigo is a powerful research tool and a knowledge-sharing community.
Digg - The best news, videos and pictures on the web as voted on by the Digg community. Breaking news on Technology, Politics, Entertainment, and more!