Tweetmeme
"Tweetmeme is a service which aggregates all the popular links on Twitter to determine which links are popular. Tweetmeme analyses links that people have "tweeted", organising and categorising them - devlivering streams of the most popular.
Discover
Using the tweetmeme button you can discover new content and tweet about it. The button provides a fully integrated URL shortener and the story or page’s title. Each link which is posted on Twitter adds increments the count on that story. The more tweets a story recieves, the more popular it is!
Share
Each tweet on Tweetmeme has a retweet button that shows the current number of tweets the story has and provides you with the means to easily retweet the link. Giving you the ability to discover new media on Tweetmeme."