Joined: 08/12/2005 07:39:47
I fear you greatly underestimate the work needed to compile this database if you ask for a single source.
It needs a huge effort to find the various sources, to bring them to a common format, to add additional information like provinces and regions, to geo code the places and to regularly update the database.
The sources used for the postal codes are listed here : http://www.geonames.org/postal-codes-sources.html
The most important updates are posted to this forum.
The use of various sources means that the quality is different for each country sometimes it is even different within the same country if we have different datasets for a single country (Switzerland for example : the canton of Zurich has released centroids for the postal code areas whereas other cantons haven't released this information.)