CAPTCHA's are those annoying pictures with characters on them that you have to type to prove to a website that you're human. They're meant to prevent automatic programs to mimic humans and spam. While they undoubtedly are a great good for the internet, they're also a bloody waste of time. The inventor of the CAPTCHA's Luis von Ahn, realised this and decided to put this human effort to good use - to convert old books into electronic form.

Listen to this interview with Luis von Ahn at the IT Conversations Network