Luis von Ahn is very entertaining and informative - you will enjoy this talk!
After re-purposing CAPTCHA so each human-typed response helps digitize books, Luis von Ahn wondered how else to use small contributions by many on the Internet for greater good. At TEDxCMU, he shares how his ambitious new project, Duolingo, will help millions learn a new language while translating the Web quickly and accurately -- all for free.
Luis von Ahn: Massive-scale online collaboration | Video on TED.com
