Tweetmeme
A Single Function SiteDescription:
Tweetmeme is a service to spot content that is posted on twitter and work out what is popular. Put simply it watches what is going on within twitter and picks up anyone posting links to content. Tweetmeme then track how many other mentions of the same content are made (and how influential they are.) and present them in a simple format.
And because the content that is posted on twitter is of a very wide content Tweetmeme also broadly categorize it, these are broken down into blogs / video / images / audio.