Frank Carver's Punch Barrel

Every now and then I bump into some software which requires input of a Zip code. Unfortunately, a zip code in and of itself conveys very little information – with the possible exception of 90210.

I was happy to find via Mapping Hacks that there is an open, public file of zip codes with a bunch of useful attributes including city, state, timezone etc.

best of all, it is self-referentially supplied in a “zip” file