There are a few areas in NZ which are great places to hang out for activities. Chief among these places are:
1. Rotorua - Taupo volcanic zone on the central North Island - close to fishing, whitewater canoeing, skiing, mountain biking trails
2. Upper Hutt - close to Wellington, this is another gem for outdoor enthusiasts with MTB, whitewater canoeing, ballooning, hiking, fishing, etc. Wellington City unfortunately never did much for me.
3. Nelson - close to this town is good fishing, mountain biking, but not sure about the skiing, whitewater canoeing. Aside from the ferry to Wellington ($70pp + $120 for a car), its a pretty isolated region.
4. Queenstown-Wanaka-Hawea is good for mountain biking, skiing, whitewater slalom, as well as as raft of other sports and activities.
These are the activity centres of NZ I believe. Queenstown and Rotorua are the easiest to get to. Direct flights from East Coast Australia - at least for Rotorua (limited) and Queenstown (expanding). I might mention that this April 21st there is the Contact Epic MTB Challenge at Lake Hawea. Every year the farmers in the region open up their properties to cyclists to go around the lake. This country needs another 1-2million, then it will be a great place to live. Sadly, its struggling to keep the people it has.