I've started my own dnsbl containing website-spammers. Here's all the relevant data:
TTL: 4 hours
Updates: 7 Minutes
So if you want to know if "192.168.1.42" is a spammer, do a hostname-lookup for: "188.8.131.52.website.dnsbl.kennmer.net"...
If it exists, he has been spamming some website within the last 3 hours. If it doesn't, everything's fine..
I'ld be very glad if you could test this as much as possible and tell me about its accuracy.. :)
Now you can also add ips to this dnsbl, yourself.. Just contact me and ask for an authorization-key..