Spam Karma 2
Spam Karma 2 is the way to go for WordPress users.
It copes with spam as painlessly as possible. Even slightly technical WordPress users like me can use this. Its goal (which it largely achieves) is to filter out as much comment spam as possible, while interfering with your legitimate commenters as little as possible. Like most such filters, it 1) approves a comment automatically, 2) removes it as spam automatically, 3) tags it for review/moderation. A related goal is to send as little as possible to moderation. I repeat that it does all these things as painlessly as possible.
Spam Karma 2 (SK2) uses rules and a scoring system to identify and filter out spam. This is easier to see than to describe, but suffice to say that SK2 uses relativelty few absolute criteria to accept or reject a comment
In my use of SK2, I end up having to review/moderate ten or fifteen percent of my legitimate comments. There are various SK2 settings and it ‘learns’ over time. If I wanted, I could probably tweak the settings to reduce the ‘good’ comments going to moderation. But I’m comfortable with it as it is.
WordPress treats trackbacks as comments, and so does SK2. This is a good thing. One of SK2’s rules rejects those annoying one-sided trackbacks. No getting annoyed with one-sided trackbacks and no more feeling guilty about not giving a newbie a chance to learn. 
You can set this criteria stronger or weaker, as you like. Me? I have set it to maximum. (Uber-techie note: During an Instalanche, if your server gets sluggish, SK2 times out when trying to check inbound posts for reciprocal links, so it moderates or rejects them.)
In sum, Spam Karma 2 has essentially solved the problem of comment and trackback spam for me. I recommend it highly.
Site Changes
Plugin Junkie
Comments - ‘Did you pass math?’ spam killer
Spam Blogs = Splogs
Who is Steel Turman?