Here an older zip code file I've been using. Not sure where I got it, but it's been very usefull. I think some file syou might be able to buy will have all the fancy zip +4 and such, but this one gets me by.

US Zip code data can be found for free with city, state and latitude/longitude info (to calculate distances) on the Census Bureau's website. http://civicspacelabs.org/ has this data along with updated zip code info they've compiled. (tab deliniated text file of this included)

A Global Gazetteer is available at http://www.calle.com/world/index.html this has latitude/longitude and a lot of other info for just about every geographic feature on the planet (outside of the US) I am currently extracting just the populated locations...cities and towns with their latitude/longitude locations and hope to find international postal code data (for free) somewhere to accompany all of this. I'd gladly share this when I'm done, but the file size is becoming quite substantial. All of the data is in the Gazatteer though. (It's seperated into files by country, but the lot of them weigh in at about 600mb compressed)

Any leads on sources of free international postal data, would be appreciated.

zipcodes.txt

US Zip code data can be found for free with city, state.

Ya But I think the idea is to enter a zip code in a field and have the city state auto fill.