It might have already been discussed here, but if you're looking for topo maps for NZ, you can download the individual sheets directly from
http://www.topomap.co.nz/
in TIFF, GeoTIFF or KMZ (can be overlaid in Google Earth) format
If you want to get the same maps on your phone or tablet (Android), you can use Oruxmaps
http://www.oruxmaps.com
a free app for viewing and caching online and offline maps, and MOBAC
http://sourceforge.net/projects/mobac
a Java program to simplify the collection of tiles from online mapping sources.
I won't go through the detailed steps, but for MOBAC,
- select Atlas type Oruxmaps Sqlite
- select Map source nztopomaps.com (New Zealand only)
- select all Zoom levels
- if you can't see NZ on your map (you have red crosses), turn on the WGS Grid and scroll to say 39 degrees S, 173 degrees E, since NZ only takes up a small part of the world
- select an area (not too big, keep to 20-30km squares or it will take ages to download), and Add selection
- hit Create Atlas, and MOBAC will create the map
- copy the map to your Oruxmaps folder and away you go