I had a lot of problems with spam on my website. The comments were section was inundated with spam messages and nothing I did seemed to block it. I eventually found some WordPress plugins which helped. I then modified them, combined them together, improved on them and then released my own plugin for blocking spam.http://wordpress.org/extend/plugins/spam-destroyer/
For the past forty days it has blocked 99.99% of all the spam on my website :) 16812 spam messages and only one wasn't blocked :D w00t!