Here is a video from WebProNews about the new Google Friend Connect API
With this, it allows you to integrate many social style interactions (Comments, votes etc) into your site. Google have created some Open Source plugins for WordPress, Drupal and PHPBB.
I will look at adding the WordPress plugin here and see how well it works.
You can find the plugins here : http://code.google.com/apis/friendconnect/plugins.html
If you know of any other plugins that have been developed, leave a comment on where it can be found.