thorpe, seeings as how Sayian is in Austin Texas, and refers to "state" and "zipcode", I'd say they're in the US, and are looking for something specific to the US...
Hey Sayian, there's been a lot of discussion about it here too, so search these boards. You'd basically need a database with all of the Zipcode/City/State combinations. From there, it's a matter of doing the DB lookups. There's plenty of resources out there that have already done the DB legwork, so use your Google, Hotscripts and these forum searches, and you should be able to find what you're looking for.