Google +1

Click the +1 button to publicly give something your stamp of approval. Others can see what you've approved in their search results, so your +1's can help friends, contacts, and others on the web find the best stuff when they search. Additionally, using +1 button on non-Google sites allows Google to tailor ads to you across the Web, based on your Google profile, +1 activity, and social connections (without sharing your information with outside websites).

In order to +1 things, you first need a public Google profile. When you create a profile, it's visible to anyone and connections with your email address can easily find it. Your +1’s are stored in a special tab on your Google profile. You can show your +1’s tab to the world, or keep it private and just use it to personally manage the ever-expanding record of things you love around the web.

+1 button API: http://www.google.com/webmasters/+1/button/