Actually, there's already a pretty exhaustive list of the recent available anti-spam options. 
I'm now going to try out Kitten's Spaminator to see if that makes a dent. (99.9% of all my spam has been going straight into moderation, but it's still getting annoying)
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1 | Beernd
Kitten's Spaminator is just great! Install her Spam Words as well, to take care of the few that still get through, and soon you'll laugh at comment spam.
2 | Jennifer
I actually already had Spam Words installed, but the two of them together do seem to do the trick. Last night, Spaminator tossed nearly 200 spam comments…. Heh. Now I just have to TURN OFF those notices the spaminator is sending!
3 | Jason Stare
What I've found, to be honest, is that the most effective things you can do is to setup a preview button and rename your wp-comments-post.php script.
Those alone will disrupt almost all of the spame you get that comes from automated sources. It won't help against those who actually spam by hand, but that's where spaminator and spamwords come in.
scriptygoddess
