anti-Spam / RBL recommendations for postfix

Hello again.

I am looking at ways to improve my spam handling in postfix as a learning experience. You will see my current smtpd_recipient_restrictions from main.cf below.

I would like to hear what if any other settings people use and particularly what other RBL. As you can see I am just using zen.spamhaus.org but I wonder if there are any better or complimantary ones I should be looks at?

smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination, reject_unauth_pipelining, reject_unknown_recipient_domain, reject_unverified_recipient, reject_rbl_client zen.spamhaus.org smtpd_data_restrictions = reject_unauth_pipelining 

nb - I have a spam solution inline so no need for recommendations there but I am think this would be good to know.