Sites to check whether your mail server has been put on any blacklists or spam lists

http://www.mxtoolbox.com/blacklists.aspx
http://www.spamcop.net/bl.shtml
http://www.spamhaus.org/sbl/index.lasso
http://www.sbg-rbl.org/cgi-bin/dnsbl/drbcheck.cgi
http://njabl.org/lookup.html