First, we determine the most popular topics that people are searching for on Yahoo!. Then, we showcase the most popular stories within those topics, based on activities like voting and emailing stories to friends. Stories with most Buzz may be published on the Yahoo! home page - you can impact what millions will see on Yahoo!.
They even have buttons and widgets to insert in your site... Gloups ! Restricted to US only !
The Buzz service borrows heavily from other so-called social news aggregators, like Digg and Reddit, as it asks users to “vote” on items they like. Items with the most votes, or buzz, will earn prominent placement.