Indefinitely: Australia (both Australian citizens and permanent residents)
For up to 6 months: United Kingdom (British citizens and other British passport holders who produce evidence of the right to reside permanently in the UK).
For up to 3 months: All European Union member states, Andorra, Argentina, Bahrain, Brazil, Brunei, Canada, Chile, Hong Kong SAR (including British National (Overseas) passports), Iceland, Israel, Japan, Kuwait, Liechtenstein, Malaysia, Mexico, Monaco, Norway, Oman, Qatar, San Marino, Saudi Arabia, Singapore, South Africa, South Korea, Switzerland, Taiwan, Uruguay, United Arab Emirates, United States and Vatican City. However, you are still required to provide: Travel tickets or evidence of onward travel arrangements; Evidence that you can support yourself in New Zealand (approximately NZ$1000 per month per person).
Obtaining a visa
If you are another national entering NZ as a visitor, student or temporary worker, you must be able to show a ticket to an onward destination or evidence of onward travel arrangements, and must present a passport valid either for at least 3 months beyond the date you intend to depart NZ, (or for 1 month beyond the date you intend to depart NZ if the issuing government has consular representation in NZ that is able to issue and renew travel documents - you should check with your passport issuing authority before travelling).
ew Zealand has a number of reciprocal working holiday agreements, allowing people in their 20s to live and work overseas, usually for up to a year. Such agreements are in place with: Argentina, Belgium, Brazil, Canada, Chile, Czech Republic, Denmark, Finland, France, Germany, Hong Kong, Republic of Ireland, Italy, Japan, South Korea, Malaysia, Malta, Netherlands, Norway, Singapore, Spain, Sweden, Taiwan, Thailand, the United Kingdom and Uruguay.
More information at Immigration New Zealand: http://www.immigration.govt.nz/