Which are the best free ‘captcha’ services available?

There are many free captcha scripts, plug-ins, packages, and other captcha based aps available. Which one is best would depend on the nature of your site and what you are trying to protect.

Many people find these captcha’s annoying and the bots are getting better at breaking them each day. If you are protecting a form, I find a text based solution to work just as well. I for instance limit form submissions to zip codes in the nearby area. This put a stop to form spam I was being hit with.