Priv3
Social networking sites like Facebook, Google+, and Twitter can track your visits to any web page that uses the familiar "Like", "Follow", or "+1" buttons, even if you do not actually click these buttons. The Priv3 Firefox extension lets you remain logged in to the social networking sites you use and still browse the web, knowing that those third-party sites only learn where you go on the web when you want them to. Priv3 does not block third-party interactions completely. Instead, it selectively suppresses the inclusion of third-party web cookies when your browser pulls in content from the social networks, but does provide them if you decide to interact with the social networking features.
