Spammers have been quite annoying for me recently, but I think I'm starting to get the upper hand.
For NetMRG's Forums we run phpBB. We've had to resort to manually approving user registrations since we get all these spammers trying to setup a user to get in our member list. Brady found a mod that kind-of extends on KittenAuth by providing a set of questions that a user has to answer in order to pass: the Anti Bot Question mod. It seems to be working very well so far - no spam registrations since I installed it. Now we just wait..
Unfortunately spammers also figred out how to spam through my comment form. That's pretty crazy since it's all custom. To be honest it was a bug since I wasn't validating a piece of data that I didn't think was form-submitted. But that bug should be silenced! Or so I hope..