http://quickfacts.census.gov/qfd/index.html (each state has it's own page) http://quickfacts.census.gov/qfd/maps/ohio_map.html http://quickfacts.census.gov/cgi-bin/qfd/lookup?state=39000
http://proximityone.com/zipequiv.htm
http://www.spatialinsights.com/catalog/downloads/products/32...