Has anyone made a Store Locator Search by Zipcode Map?

Hey,

I'm in a project where I need to develop a map that searches for a nearby store when someone types in their zip code. An example of this can be found here: http://www.jimmyjohns.com/findAJJs/findAJJs.aspx

Has anyone ever made one of these? I've been searching the web and found tons of sites (basically any big retailor) who uses this function but no documentation on how to do it.

thanks.