Askimet to a degree. Though, to be honest, IP bans are largely ineffective because one could just change their IP immediately. Ex. I have a button on my modem that instantly changes my IP address when pushed. It can go from something in the 74.*.*.* range to something in the 96.*.*.* or even higher.
I know where the place is to blacklist comments and stuff… but, how do you get the IP of the spammer? The one that keeps registering on one of my sites hasn’t got a chance to comment or anything because I delete it like instantly.