I installed Akismet.
WordPress has pretty good spam-defense options included by default and since 1.2 I did not have any spam comment slipping through my gates. However, the number of spam getting in was getting on my nerves - I still had to go to moderation queue and clean the mess up.
Thus I’m trying out this. It’s looking good so far, with only one false positive; which btw, really looked like spam - it took me good 30s to realize it is not a spam. I’ll give it a daily look in the next few weeks and if keeps working nicely as it is now, I will relax and not care about spam comments anymore.