StumbleUpon
StumbleUpon is a web browser plugin which was founded by Garrett Camp, Geoff Smith, Justin LaFrance, and Eric Boyd during Garrett's time in post graduate school. It gives an user to rate webpage, photo, videos and articles. StumbleUpon also helps user discover and share high-quality pages matched to users personal choice. These pages can be recommended to users by their friends, the one who shares similar interest. Users rate the sites they like which automatically shares them with like-minded people and helps them to find new friends. StumbleUpon selects which new webpage to display based on the user's ratings of previous pages or ratings done by his/her friends, and by the ratings of users with similar interests. StumbleUpon members amount to 3.68 Million.

StumbleUpon is a social networking website which also have the ability to rate and review each other’s blogs. Users can also join interest groups, which are community forums for specific topics and then members can post comments on particular topics, it is much like a discussion board in these groups and also provide links to websites that contains material to the specific topic.