ZIP code radius search?

[greenie2600]

Hi guys -

I'm putting together a quote for a site that will allow users to submit events to a calendar of events. Users will then be able to locate events by entering a ZIP code and a radius (e.g., within 5 miles, within 10 miles, etc.).

My question is: how can I determine what other ZIP codes are within x miles of a specified ZIP code?

Are there any free web services that provide this information?

[HalfaBee]

I found this zipcode DB using google.
http://www.free-zipcodes.com/download-zip-code-database.php

A bit out of date (2006), I am sure there is a thread about the calcs for distance in the forum.

[Weedpacket]

Try searching in the forums for zip code radius. This has come up before and there are lots of different solutions to be found.

[bretticus]

This came up for me a several years ago when my work wanted me to consume noaa.gov xml for weather data. Unfortunately the world is round and so I found somebody's post about using the grand circle equation as a custom mysql function. Very useful I must say. Here is a useful post on it also.