Social News finds users' Facebook friends who are also reading the Huffington Post and links them together so they can discuss the story in greater depth.
The US-based politics and current affairs website attracts over 1.7m comments on stories every month -- with some stories drawing as many as 10,000 comments.
Social News automatically creates a personalized profile page for users to keep track of their friends, showing who is commenting or reading stories, or voting in polls.
The information is posted in the users' Facebook stream, their Social News profile, or a separate widget that appears on every Huffington Post page.
Arianna Huffington, the Huffington Post editor, said "think of it as HuffPost's new digital water cooler."
She said: "News has become an important element of community -- something around which we gather, connect, and converse. And we can all become part of the evolution of a story now -- expanding it with comments and links to relevant information, adding facts and differing points of view."
Users retain complete control over what stories and comments are shared with their Social News friends, as well as what is posted to their Facebook Wall, and into their Facebook stream.
What is being read will not appear on Facebook unless the "Like" button or the "Facebook Share" button is used.
Users can also place themselves in "Stealth Mode" before reading stories.