The links listed below are the travel tools that we actually use when we travel New Zealand plus a couple of others we thought you may find useful (as you lot generally come from exotic overseas lands).
The quality of information improves dramatically as you get closer to your destination. However, i-sites (the NZ visitor centres) as well as other entities (hotels and operators) may also have commercial reasons to recommend or not recommend operators. The level of commission paid, the size of the xmas hamper, whether or not the operator can afford the usually sizable fee to display brochures in an i-site in the first place, can all consciously or unconsciously affect the enthusiasm of the recommendation.
So be aware of that. We use a mix of google NZ, the i-sites, but in particular the brochure racks of backpackers in the area. If you are at a distance, email the accommodation you are booked with and ask for their opinion. In our experience the desk staff of local accommodations will bend over backwards to get you the best advise as it means you recommend their accommodation to others. The free market verses the fee market.
Various
Mobile phones - Everyone knows about Vodafone and Telecom, but 2degrees may well suit travellers a little better. Cheaper rates and various cool international deals too. And at last SIM cards being sold in NZ for an acceptable price, hooray.
Transport
Flights
House of Travel - Brilliant site that compares airlines to find the cheapest domestic flights within New Zealand. Sometimes they even sell flights cheaper than the airline does on its own site. Alchemy?
Train
Enjoy the spectacular scenery of New Zealand by train, whether through mountains or along coastlines. No better country to have such slow trains.
Bus
InterCity Coachlines - This is the big one; New Zealand's largest coach network. Don't forget to look for all the wee operators that ply (mainly) the main South Island routes too, see below. Note that often for some bizarre or perhaps commercial reason the nations i-sites seem to be unaware of the plethora of other options available. Use google!
Some of the other buses, see brochures at backpackers for others, or google search.
atomic shuttles, west coast shuttle, Knightrider, naked bus, tracknet (Queenstown-based track-head service).
Boat
Inter-Island Ferry across the Cook Strait between the North Island and the South Island - The big guys - The little guys
Accommodation
YHA
The world wide non-profit backpackers hostel network. Pretty sharp accommodation in the cities, gets more character-ful as the towns get smaller (a nice thing we think!). Our absolute favourite is Opoutere in the Coromandel.
BBH
Budget backpackers hostel network around New Zealand. Generally (but not always) smaller hostels with independent owners who are doing it because its just in their nature!
Bed and Breakfast Accommodation
Find bed and breakfast accommodation around New Zealand.
Book a Bach
Find holiday accommodation the way kiwis do. Bach is the kiwi terminology for holiday house, historically a shack by the beach, but these days can mean just about anything.
Weather
Met Service
Find out what the weather is going to be like at the places you're going to visit.
Met VUW
Forecast charts for the weather geeks amongst us.
Currency
Yahoo Currency Converter - See how your currency compares to the New Zealand Dollar.