Google have recently started to include more information from people you know—stuff they’ve shared on Twitter, Flickr and other sites—in Google search results.
Google have announced taking that a step further, enabling you to share recommendations with the world right in Google’s search results. It’s called +1—the digital shorthand for “this is pretty cool.” To recommend something, all you have to do is click +1 on a webpage or ad you find useful. These +1’s will then start appearing in Google’s search results.
Google said they will be slowly rolling out +1’s, starting in English on Google.com. If you can’t wait to start seeing +1’s, we’ll soon let you opt-in to the launch by visiting our experimental search site. Initially, +1’s will appear alongside search results and ads, but in the weeks ahead they’ll appear in many more places (including other Google products and sites across the web).
More: http://googleblog.blogspot.com/2011/03/1s-right-recommendations-right-when-you.html