If anyone is interested in developing a similar service, then you can use the (free) zip code information provided by the US Census Bureau: http://www.census.g

If anyone is interested in developing a similar service, then you can use the (free) zip code information provided by the US Census Bureau: http://www.census.gov/geo/www/tiger/zip1999.html http://www.census.gov/geo/www/tiger/zip1999.html However, please note that some information may be outdated. The US Postal Service now maintains the zip code data sources, but I'm not sure if you must pay for it.