We've released a new application in our zip code arsenal for displaying a single zip code boundary:
www.usnaviguide.com/zipencoded.htm
This page uses the Google Maps Encoded Polygon method, so as you zoom in for a closer look, the details of the boundary increase and zooming out for a broader view shows less and less detail.
A license to this system can be purchased for $7,000 which includes the page, the server program, the zip code polygon database (unencoded) and the encoded database along with a database of every zip code identified with name, point (if possible), county, state and other information.