Found good blacklist checkup sites yesterday. Nice to know there are still some out there willing to help out troubleshooting wihtout charging you (unlike dnsstuff.com does now).
http://www.mxtoolbox.com/blacklists.aspx
http://www.blacklistalert.org/
Both do a good job of looking for you. Blacklist alert also verifies you have a good reverse dns entry (so you can send email to AOL).