To view on a map any of 2,507 postal area boundaries at full resolution (as defined by the Australian Bureau of Statistics for Census 2006 population and housing data) just follow this simple URL pattern:
Multiple postcodes can be added to the map as follows (at this stage one at a time only):
A set of simple instructions on how to configure other map parameters can be found on aus-emaps.com web widgets page.
And this file will also be handy to script the functionality: list of postal areas (Census 2006 version in csv format). Please note, Northern Territory postal area boundary data are named with leading "0" (ie. 0800).
More examples of use of Reference Map service
Australian Postcodes User Guide
Post code maps and population statistics
Free postcode search widget