MT-Blacklist/Comment Spam Clearinghouse: MT-Blacklist/Comment Spam Clearinghouse. This is the central database that is a short term fix. You can both download this manually (ugh) and also submit new spam.
For instance, today, I got a bunch of spam that the database didn’t pick up. If you install then, you need to submit new spam entries to them via a “spam form”:http://www.jayallen.org/comment_spam/submit.