If you switched over to WordPress, I know they have all kinds of spam plugins. Unfortunately, when I tried to implement one on my site, I was killing everybody's comments... I couldn't figure out why it wouldn't let the ones I listed as approved, get approved.

So now I use nothing. But I do have my comments closed after a certain number of days (older ones which the spammers used to target) and I haven't had any spam in a long time.