I am trying to implement something a bit more simple than the damned captchas to fight the comment spam. They have worked very well for everything except for manually entered spam comments which I can just delete myself but the captchas are difficult for everyone including myself to see. I am going to use a simple Comment Challenge (eventually) and a couple of other things. One major change is that if you don't have JavaScript turned on you won't be able to comment.
I have disabled the Captchas but have not rebuilt the 5000 or so entries so if you are on an entry other than this one prior to 10pm or so you may get an error when trying to comment.
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I wrote a plugin (for Wordpress though) to block comment spam without resorting to captchas called WP Captcha-Free (Sorry for the shameless plug, I hope you dont take this as comment spam ;). It uses a combination of time based hash and ajax to block spam. I use it myself of both my blogs and now get zero spam from an earlier 40+ per day. You can check it out at http://wordpresssupplies.com/wordpress-plugins/captcha-free/
I would check it out but this site doesn't run Wordpress.