This summer, our forums were inundated with spam. Lots and lots of spam. Because I can't mail the spammers a crate of mosquitos, I made a CAPTCHA that only they can see, and that can't possibly be answered correctly. [more inside]
CRAPCHA stands for Completely Ridiculous And Phony Captcha that Hassles for Amusement. It doesn't keep spammers out. It doesn't crowdsource book scanning either. CRAPCHA's only job is to baffle users, and you can add it to your site today.