Zip Code Guy provides detailed zip code maps for every county in the U.S. You can choose by state or individual county, or buy maps for the entire country. They are also offering a special free U.S. zip code database.
For those of you who are wondering “Why in the world would I want information on zip codes?”, targeting marketing campaigns by specific areas based on demographics is highly effective. For instance, you may be marketing a specific high-end service in a metropolitan area, so targeting to only the high-income zip codes will save you a lot of money and time.
There are multiple uses for zip code information. E-Commerce store owners can use the information to research potential credit card fraud issues, or match postal zip codes to cities.