reCAPTCHA seems to be making the rounds quite widely right now, but I thought it was too neat to not mention it. Reminiscent of Amazon’s Mechanical Turk, reCAPTCHA is a clever way of distributing the word-recognition work involved in scanning old books, and, at the same time, providing humanness-credentials needed to foil spambots. And it’s accessible, too (though there’s no OCR benefits from the audio version)!