Captcha with a purpose

Captcha is the name for the distorted words that you have to enter on some websites, such as ticketmaster or blogger, to verify that you are a real person and not an automated bot.

Wired magazine reports in the July 2007 issue (article not online) that the inventor of captchas, Luis von Ahn, is creating a new version of captchas that include two fuzzy words. One word is the control word used by the computer to verify a human user but the other is a word from Internet Archive's book scanning project, the optical recognition software failed to indentify. A pretty ingenious way to clean up a scanned text, in my humble opinion.