USNaviguide/Maps.huge.info has three versions of zip code polygon databases available for licensing:
2006 ZCTA - $1000
This is the most popular option as the areas are fairly up to date, accurate and inexpensive.
2007 USPS Zip Code Areas - $5000
This option has the most up to date polygons. All zip codes except "point" (p.o. boxes, APO's and buildings with their own zip code) zip codes are covered. This database is updated quarterly and is best used by those that require the highest accuracy and up to date data.
2000 ZCTA - $200.00
These polygons can be obtained for no cost directly from the census bureau in several formats, notably, shapefiles. We provide them at a nominal charge of $200.00 in a tab delimited Postgres dump format. I suggest that the effort be made to download and extract the data yourself though, as it is a useful exercise. The downside of these polygons is they are very out of date, circa 1998 or older, so unless you need to match your zip code areas to specific Census 2000 data, they are probably useless.
We provide 2006 ZCTA and 2007 USPS polygons in two formats: shapefiles and tab delimited Postgres dump formats. The dump format loads easily into Microsoft SQL Server and MySQL, plus of course Postgres so is the usual choice.
To license any of these databases, please contact us ( click here ) directly for instructions on how to submit payment and downloading.