Duolingo is a free language-learning website and crowdsourced text translation platform. The service is designed so that as users progress through the lessons, they simultaneously help to translate websites and other documents. As of March 2012, the site offers Spanish and German courses for English speakers. They plan to add French, Italian, and Chinese. Duolingo launched in private beta on 30 November 2011, and has accumulated a waiting list of more than 100,000 users. As of 19 January 2012, the service has translated over 45,000 sentences.
Intro (Youtube):

check it out: http://duolingo.com/