Ocr

http://live.gnome.org/OCRFeeder software for automatic layout analysis and optical text recognition (GTK-based, possibly cross-platform)

http://n3on.org/projects/reCAPTCHA/ A paper [presented @ DEFCON 2010] describing algorithm to solve reCAPTCHA ( http://reCAPTCHA .net )

http://habrahabr.ru/blogs/artificial_intelligence/74326/#habracut Different approaches in using neuron networks for OCR (optical character recognition) – an article in Russain

http://recaptcha.net/learnmore.html cool CAPTCHA that is used to OCR books