Long ago, I decided to create a regional Directory ( http://etalii.info ). One that will list any site, from anywhere, and categorize each by their own city. Because I own 19 Directory websites, I get tons of submissions every day. My goal is to add any site that contains full address information to this regional Directory, and it is expanding very rapidly both in popularity and Alexa ranking.
I also decided to add an extra field to this Directory to list the county that the business resides in, and to make this field searchable. This way, visitors can do a search for all businesses in a particular county.
The problem was that I haven't found any businesses that list their counties on the website. It was easy to find the solution: http://uscounties.com/zipcode_finder.html
With this tool, I can easily look up the county by simply searching the zip code.
This may seem like a lot of work, but I believe it is worth it. I have found that if you use the tools available, and you are willing to put the time and effort into the creation of a quality site, it will pay off in the end.