Stop spam without captcha

Question

I want to stop spammers from using my site. But I find CAPTCHA very annoying. I am not just talking about the \"type the text\" type, but anything that requires the user to

Answer 1

How about a human readable question that tells the user to put in the first letter of the value he put in the first name field and the last letter of the last name field or something like this?

Or show some hidden fields which are filled with JavaScript with values like referer and so one. Check for equality of these fields with the ones you have stored in the session before. If the values are empty, the user has no javascript. Then it would be no spam. But a bot will at least fill in some of them.