Stack Overflow is a wildly successful question/answer similar to Experts Exchange. Users can ask and answer questions, rate each others' contributions, and earn karma points for high quality participation on the site. This type of functionality touches on many popular social media features and integrates them into a seamless whole. We'll be duplicating Stack Overflow's functionality using Drupal and show you how we've done it.
Fantasy Site: Stack Overflow - Diwd '09