check if valid us entry

Does anyone have any validation written on how to check that a entry is a valid us entry based on zip, state, and area code?

Something like this might require a plugin, and it might cost some money.
I did a few searches, but I believe you want to check to see if the zip code is valid.
This is tricky, you might need a large database or something. I wouldn't know where to begin on something that seems like it's used by a lot of web sites.

You can try too:
http://www.aspin.com/func/search?tree=aspin&qry=zip+code&cat=all

Thanks Aspin.com