Certainly, there have been plenty of SPAM detection hacks and plugins available for WordPress. I thought that I would jump into the fray with my implementation.
SA-Blog is a WordPress plugin that requires a working SpamAssassin 3.x installation. I've only tried this on Linux, but it should work (or be easily ported) to other Operating Systems.
I put a hard-stop to any message that ranks as SPAM and display an error. Any SPAM message is not accepted and must be re-written before the comment can be added. The moderator shouldn't have to delete messages that are clearly not wanted.
Click here for a short setup guide and a link to the files if you are interested.