GeoNames.org, UnitedStatesZipCodes.org and Globefeed.com are some of the websites that offer a list of postcodes. These sites provide lists of all the postcodes within the 50 states of the United States.
GeoNames.org lets users search for postcodes for any state. It offers a huge list of states and cities from which the user can select and view the postcodes.
Globefeed.com is an online tool that displays a postcode in the United States when the user enters the location consisting of a place, an address or a city. UnitedStatesZipCodes.org allows users to search postal codes by ZIP code or by address, city or county.