Shareaholic is the perfect Firefox extension for all those online bookmarking services 'junkies' who like to share just about anything interesting they find on the web.
After installing Shareaholic on your browser, you'll get a new button in the toolbar from which you'll be able to add any website to some of the most popular bookmarking services such as Digg, StumbleUpon or Del.icio-us, plus sharing it through other social networking and microblogging sites like Facebook, Tumblr or Twitter. The aim behind this extension is to make link sharing easier for you, so you don't have to load your favorite social bookmarking sites every time you find something interesting. Plus, you can also check the links other people sent in and find new interesting stuff everyday.
What puzzled me about this extension is that apparently it has some kind of connection to a link sharing site called Bzzster, but this relationship is not clearly explained anywhere in the extension's documentation.
With Shareaholic you can share any interesting link in a much easier way, using the most popular online social bookmarking resources.