Stop Forum Spam looks nice. It's great they're giving the data like this. In fact, I'm somewhat surprised there's no software download to self-host. Seems rather easy to make, given the data files.
Are there any other filters you recommend?
This was already my list of "approved" spamfilters :) I don't know any others that I like and are low in false positives.
I'm wondering how much a Hashcash implementation would help. The approach doesn't seem to be widely attempted. Maybe because we assume spammers are using botnets anyway and don't care about computational cost?
It seems this is part of the automation, it got flagged based on this.
By the way, I am quite happy with JavaScript based spamfilters, they work quite well for small websites. The service Stop Forum Spam is something that seems fit for this, also at bigger scale. I assume Akismet might be good too, but it is somewhat leaky in privacy, depending on what you send to it.