I've recently written a brief guide on fighting spambots and spam registrations on PHPBB forums. I thought some of you may be interested and find it useful, i hope it helps! http://www.quickwhois.co.uk/blog/phpbb-stopping-the-spam.html If you find it useful, please feel free to Digg, Stumble etc
EGS, if you still use PHPBB try the 'user must have made X posts before posting URLS' mod, seriously it cuts 99% of all spam....
That's a great article. The main reason why I still use Phpbb is because of the mods. The main one is the seo friendly url mod that gives url's .htm extensions for the search engines.