reCAPTCHA
reCAPTCHA is a CAPTCHAw system using two words. One of them is a known control word, the other is an unknown, un-OCR-able word scanned from a text in the process of being digitised. The form requires only that the user gets the control word correct - the other word is assumed to be correct based on this. The results are fed back to reCAPTCHA, who compare several interpretations of the same scan. Once there is sufficient confidence in the word, it is committed to the digital version. In this way, scanned texts can be human-converted in a distributed fashion.
Tags: CAPTCHA, UI, web
