Shinyubin is a Kotoeri dictionary that matches Japanese ZIP codes to their addresses. That means that if you input, for instance, "2120023," you will Get "神奈川県川崎市幸区戸手本町," which is exactly the location that that ZIP code defines according to the Japanese Post Office. If you need to input a lot of Japanese addresses, this dictionary could be very helpful to you.
What is Kotoeri? Kotoeri is the standard Japanaese input method for Mac OS X. This dictionary will not work on Windows, or with other input methods like ATOK.
Random trivia: The "ZIP" in "ZIP code" stands for "Zone Improvement Plan" (source: Oxford American Dictionary). It's an acronym, so it should be capitalized!
2010-01-07
Zipcodic converter rewritten in PHP. Now provides more thorough listings.
Shinyubin dictionary current as of H21-01-28