Jeff Capron wrote in to say he’s written a plugin to use Akismet for vBulletin. The site requires an email to check it out, so I haven’t tried it out myself, but if you use the very popular vBulletin forum software you may want to check this out and let us know how it works in the comments.
For vBulletin
Akismet 
This should be an awsome plug in I love the bulletin board system Vboard offers and use ot on several domains.Well plug it in and see how well it works for sure. But if Jeff made it I am sure it is bug free!
=)
Do we know when this will be available? I would like to announce it on http://www.vbulletin-faq.com
Nice spam joey.
It was released several days before your post.
A bit late, I know, but this does work; and quite well at that 🙂