Automate data entry with Web services and Ajax

A little background on the idea
The United States Postal Service (USPS) has made several Web services available (see the USPS Web tools sidebar). One of those Web services accepts a ZIP code and returns the corresponding city and state. In this example application, you make use of this CityStateLookupRequest to save the user some typing. This feature also gives you better address data in your database, because you reduce the chances of typing errors.
Prerequisites and assumptions
David Heinemeier Hansson, the ideological spirit and creator of Ruby on Rails, is a smart guy! In RoR, he implemented a number of great ideas, ideas that make developing Web applications much easier and, as a friend of mine remarked, ?It makes programming fun again!? There?s little doubt in my mind that other frameworks and programming paradigms will espouse these ideas.