We've been hearing a lot recently about responsive design as the recommended approach for companies who want to become mobile-friendly.
Kristina Kledzik recently wrote a post here on the SEOmoz blog about responsive design and why it’s often the best option when creating a mobile-friendly online experience. She discussed its advantages in dealing with usability issues, duplicate content, mobile search rankings, and link building. Google recommends using a responsive website design where this makes sense from a user perspective, and Bing encourages a "one URL per content item" approach.
Via Antonino Militello