Since a couple of days my blog is the target of a spammer in the comments. A quick search on the internet pointed me to Nio's Weblog where I could find the Anti Spam Image plugin for WordPress. So, from now on, when you want to post a comment on one of the items here, you need to type in the code in the image. I hope this will help prevent spam in the comments in the future.
Have you tried to use Spam Karma: http://unknowngenius.com/blog/wordpress/spam-karma/
I use it on my blog and it is very effective in fighting spam.
I also like this Anti Spam Image thing. Thanks for sharing. I will give it a try also.