I guess I’m a late adopter, but WordPress.com offers a comment spam service called Akismet. I had never bothered to register as a user so I could enable the spam filtering on this site. But then yesterday I did. And it rocks. I was moderating dozens if not hundreds of spam comments a day, weeding through to find the few real comments every month.
Today, I checked into the moderation, and there was a real comment… and Akismet had caught 204 spam. I skimmed through the first 150 caught spam, saw that it all really was spam, and hit a single button to delete it all.
Fabulous.