You've got a Friend Connect gadget(Adsense)

Social networking features are all the rage these days. (AdSense has even joined the trend with Twitter!) Now your site can be part of the social web by using the features offered through Google Friend Connect to awaken and strengthen your community of visitors.

With Friend Connect, your visitors can join your site using credentials they've already created with Google, Yahoo, AOL, and others, and link in the people they know on services like Google Talk, Plaxo, Twitter, and more. There's also a gallery of gadgets where you can choose from features like commenting, ratings and reviews, and the social bar to add to your site. Just like AdSense, you can simply copy and paste a few snippets of code to add these features to your site. Or, if you want to do some deeper integrations, you can use the Friend Connect APIs.