try
www.spampal.org
- it uses a lots ip-bases, where spam comes from (osirusoft, spamhous, spamcop, spews, formmail.relays.monkeys, easynet blackholes, spambag, and more and more..) - so you could choose which DB is most suitable for you. it even allows to block whole countries like: china, korea, russia, japan, brazil, nigera, etc, etc.
i've turned off some agressive dbs like: spews & osirusoft , and it works very good for me (filters about 95% of spam)