Catherine Hampton's SpamBouncer has a zillion blacklisted domains:
http://www.spambouncer.org/webdev/downloads/beta.shtml
1. download sb-new.tar.gz
2. mkdir sb; cd sb; tar xfz ../sb-new.tar.gz
3. perl -lne 'print "$1.$2" if /)([\w-]+?)(.*?)([a-z]{2,4}?)(/' *.rc \ | sort | uniq -c | sort -nr
I suspect Catherine has a list in raw format (for all I know, there are some whitelisted domains somewhere in there). Merging it with WS might make sense. Catherine is probably a bit (*cough*) more aggressive than you.
Also, many domains are listed more than once. I'm guessing that they're worse in some way. Or something. ;-)
Daniel