Anyone that hasn't seen the property tax series that the Atlanta Journal Constitution is doing, start checking it out. They are giving Metro Atlanta taxpayers reason to appeal property taxes, as well as some (limited) market data to use.
http://www.ajc.com/news/dekalb/atlanta-property-taxes-north-785162.html
http://www.ajc.com/news/dekalb/atlanta-property-taxes-north-785162.html