The following are what I use as reasonably good yet conservative values for DNS blacklisting and RHS blacklisting.  Comments?
RBL:  zen.spamhaus.org:whois.rfc-ignorant.org:dnsbl.njabl.org
SBL:  bogusmx.rfc-ignorant.org:multi.surbl.org:black.uribl.com:ex.dnsbl.org