ReCAPTCHA – A great idea to make entering all those CAPTCHA codes usefull.
Now, I hate the idea of CAPTCHA in general. Having to enter cyptic codes to verify you're a human is a not the best idea that has come around. I can't tell you how annoying it is to have to enter CAPTCHA codes when you're logged into Blogger and want to post a new post. I've logged in,, I think that's enough to verify I'm a human. But obviously bots can log in too. Anyway, they are annoying and waste useful time.
ReCaptcha takes all those codes you enter on every form and helps solve words that can't be deciphered via OCR to help complete digitization of real books. If that's not a good enough explanation visit Recapture.
I don't use CAPTCHA codes on this blog just because I hate them but if you do maybe consider using Recapture. They have a wordpress plugin you can use if you do use CAPTCHA's on your comment forms.
They're Slogan is “Stop Spam, Read Books” – it's so great.