Google has announced that they are experimenting with mobile search. They've indicated that when users are using their smart phones to search, website that are "mobile friendly" will have higher ranking for relative search terms. This means if your website design has been optimized for mobile screens, including sites that are designed with "responsive website code", that site will appear higher in the results pages.
This is good news for responsive design websites. Getting a boost from mobile search results only means more business for those sites with mobile -friendly sites.