Map-Logic are using Google Maps to provide a number of free online Postcode Area and District boundary maps for Great Britain.
Users can view different region maps of Great Britain, view the extent of Postcode Districts in each region and click on the map to retrieve the district's postcode.
Map-Logic say that at the moment they haven't worked out a way of showing all the labels for all Districts at the same time, so to retrieve a region's postcode you need to click the region on the map. Another omission is a search feature. It would be nice to be able to type in a postcode and be shown the relevant region on the map.