I've made some dramatic progress with my Zip Code data. Yea I know, when is the old fool going to stop babbling on about crap like Zip Codes, Counties, FIPS and all that other nonsense? Sorry, it's what's keeping me sane right now and if you want to tune out, bye!
Still here? Ok, the thing about Zip Code data maintained by the government is that they never associate a State much less a City to the Zip for some reason. It's just a number with geographical boundaries which happen to intersect with a City inside a State. So I did some research and found an API that provides that missing info and completely rebuilt my Zip Code database.
152 Zips from my initial dataset were determined to be invalid for various reasons and I now have 32,992 verified Zip Codes, each with a City and a State. This means I can write tools that query the data in a variety of ways, like show me all the Zips in Seattle, or all the Zips in Tennessee, or all the Zips in Utah Cities that start with "Ce". You get the drift...
Now I'll go write some code. (Update: Try this and click on a State or two.)