The Ministry of Health recently released the Altas of Socioeconomic Deprivation (NZDep2006). PDF maps are available from this Atlas's homepage on the Ministry's website, but shapefiles aren't directly available from the website. A free CDROM is available that contains shapefiles - as well as all the reports. I received my CDROM a couple of days ago and it contains the following layers - CensusAreaUnit, DistrictHealthBoard, NZ_Outline,NZDep2006, and TerritorialAuthority.