Social bookmarking is an online service that allows online users to share their content with backlinks to their website. There are lot of bookmarking sites from long time. Like- Digg, Delicious are very old site for bookmarking.
TechnologyMagnet.com is a free social bookmarking platform that allows users to submit their content with a backlink to their website. Services like- add a website, submit URL, free directory, social bookmark are available here.