Google introduced “Google Buzz API,” that “aligns itself with ever-growing family of freely available and community-developed protocols, formats, and standards for sharing and consuming social content on web, including ActivityStreams, Atom, AtomPub, JSON, OAuth, PubSubHubbub, MediaRSS, PortableContacts, and more. We’re already excited to see developers who were helping us test API deliver terrific apps. Today you'll start seeing following sites (see pic) and services integrate with Buzz. End-users opt into using apps built with Buzz API via an interstitial confirmation screen outlining the apps requested access scope (read-only, read/write, etc.). They can see which apps’ve access to their data and can disable access at any time from Google Accounts page, Google Dashboard, “Buzz" tab in Gmail Settings, or from app itself. Initial iteration of API includes support for fetching public per-user activity feeds, fetching authorized and authenticated per-user activity feeds (both what the user creates, and what they see), searching over public updates (by keyword, by author, and by location), posting new updates (including text, html, images, and more), posting comments, liking updates, retrieving and updating profiles and social graphs, and more,” writes Google.
More Info: Buzz Apps