I'm curious if you've tried something like Mollom ( http://mollom.com/download ) for spam control. I'm not sure if it's able to be implemented on PHP boards like this but there is a PHP library for it. I know it can be implemented on a Drupal comments system (since I'm a Drupal dev that's kind of easy for me to imagine implementing). Anyway it's a state of the art system that has a continually kept up blacklist and some pretty smart captcha logic built in, but I don't know if it'd work for what you have going here.

Barring that, I was wondering if you were going to keep the PHPbb format or possibly upgrade to something a bit more maintainable. I don't hear a lot of good things about PHPbb security but as far as I can tell they're easier to implement from scratch than a lot of CMS solutions like Drupal that require some studying up. If you ever want to consider a Drupal install, though, hit me up on IM/email and I can give you some advice, it's not actually too hard to keep up a low-level community site on Drupal and it's pretty dang secure and easy to proof from spammers!

Long story short: hi, I'm a fan! Love what you're doing here. I'm a part-time novelist that needs a place to just play around and throw down something tasteless and fun. I might write something here but I don't want to get lost in the spam flood, wow.