"Google Friend Connect lets you grow traffic by easily adding social features to your website. With just a few snippets of code, you get more people engaging more deeply with your site."
"Websites that are not social networks may still want to be social. But the barriers to offering social applications on the site have been considerable. Google Friend Connect changes this by enabling any site to offer dozens of social gadgets created by Google and OpenSocial developers to their visitors. This means more visitors spending more time on a more engaging website — with absolutely no programming required to make it happen."
You can read here for more information.
Please note: this "Google Friend Connect" is a beta preview release.
Hope this useful.