Do you have a WordPress blog? Are you using the free Akismet plugin? Why not?
This baby stops comment spam in its filthy tracks, my friends. You need to get a (free) WordPress API (they tell you how to do it, it’s easy), then you install the plugin…done. It works so well that after about a month of testing I removed moderation from my comments! In roughly three months of use it’s stopped nearly a thousand spam comments, and has only allowed one questionable posting through.
I mean it: Akismet works!
The only down side I’ve run across is the occasional false positive. Some of my guests have left legitimate comments with links included, and maybe one in ten of those gets nabbed. I find it no chore at all to review the spam queue before I nuke ’em and make sure nothing good is in there.
On your WordPress plugins control page just search for Akismet and take a decisive stand against comment spam!