ReCaptcha

Did you know that by filling out ReCaptcha captchas, you are actually contributing towards the digitization of books?

ReCaptcha started as a project at Carnegie Mellon that aimed at digitizing books. Captchas were already in implementation by then, and they recognized that a lot of human effort went into solving captchas every day around the world. They figured they could put this human effort to “use”.

ReCaptchas give you two words to solve. One word, they have the answer key to, but the other is an unsolved word from books and such, that they seek interpretation for. People like you and me solve the two words, and the system assumes our answer for the unsolved word is correct. They then present the same unsolved words multiple times to different users, and have a confidence rating in place to verify accuracy.

So, the moral of the story is, if you have a website that you want to protect from spammers and robots, use Captchas. And, if you want to do good while using it, use ReCaptchas!

Reference Source: http://recaptcha.net/learnmore.html