I ran across a tutorial about how to make a fairly clever CAPTCHA where solving it relies on clicking on a particular part of the image rather than filling in a field. While the concept itself is clever, the implementation given in the tutorial is not (requiring the user to click on a particular color). The problem with that is that computers are very good at knowing the colors of things too.
So just for fun (and to see if I could do it), I wrote a script that beats the CAPTCHA each and every time and in the process submits fake spam to the form it’s attempting to prevent (I know, I’m an evil dirty spammer ;)). If you’re interested, read their tutorial first and then check out the rest of this post for how to beat it.