I started work on a web app that makes extensive use of zip codes recently.
The trouble was, I couldn’t get my hands on a good listing of all the zip codes in the United States without paying $20 or more at some fly-by-night website.
See for yourself here
A FREE CSV file of all US ZIP codes including zip, city, state, latitude, longitude, and county.The date says it was last updated on September 20, 2007, which gives me hope that the file is frequently updated.
Many Thanks to ibegin! Enjoy!
update: The list was updated January 18th 2008