There is a pool of servers at nz.pool.ntp.org, which provides Round Robin DNS access to publicly accessible NTP servers that have agreed to be part of the pool.
Many ISPs have NTP servers for their customers:
Some universities have publicly accessible servers:
For a long time Waikato University had public NTP servers. They are still available but no longer publicly accessible.
You shouldn't synchronise to a stratum one server for your small network -- if everyone did that then the server would need too much bandwidth. The difference in accuracy between synching to a stratum 1 server and a lower stratum server is negligible! 
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There are three stratum 1 NTP servers provided by .nz Registry Services (NZRS) for network operators based within New Zealand. more
All three are Symmetricom S300 NTP servers, each connected to a differential GPS antenna on the roof and each with a rubidium oscillator to provide a stable clock in the event of an issue with the GPS signal. more
The standard for time in New Zealand is maintained by the Measurement Standards Laboratory, part of Industrial Research Limited. MSL runs several public NTP servers that are referenced to UTC(MSL).
They are FreeBSD-based servers that are directly connected to their master HP5071A caesium clock. more
pool.ntp.org has NTP server pools for many countries.
The US National Institute of Standards and Technology (NIST) operates several publicly accessable stratum 1 time servers on the pacific coast of the US. These servers are referenced to UTC(NIST) using the NIST Automated Computer Time Service (ACTS), a modem-based service established in 1988. more
The US Naval Observatory (USNO) operates several stratum 1 time servers from it's Alternate Master Clock Facility (AMCF) at Schriever Air Force Base, near Colorado Springs, on the same site as the GPS Master Control Station. These servers are referenced to UTC(USNO). more
Hurricane electric operates several stratum 1 servers with good connectivity on the pacific coast of the US. more
The Australian National Measurement Institute (NMI) maintains the Australian time standard, UTC(AUS) using caesium and hydrogen maser standards. NMI maintains a number of NTP servers which are referenced to UTC(AUS). To use these servers, you need to register via email. more
GPS time signals have an accuracy of ±10ns, making them the best option for most applications. The planned establishment of Galileo by the European Union and Compass by China will provide additional sources of time for compatible receivers.
It's possible to sync a computer directly to the Pulse Per Second (PPS) output of a suitable GPS device using a serial or parallel port more. For better accuracy, there are PCI cards available with PPS inputs and/or built in GPS receivers. There are a variety of dedicated NTP servers available, some with internal oscillators that can maintain a stable clock if the satellite signal is lost.
If you require better accuracy than GPS can provide, OmniSTAR provides GPS and GLONASS correction data via a worldwide network of geostationary satellites and reference stations.
It might be possible to receive the 5, 10 and 15 MHz signals broadcast from NIST's WWVH facility in Hawaii. WWVH continuously broadcasts a time code on a 100-Hz subcarrier. The time code presents UTC(NIST) information in Binary Coded Decimal (BCD) at a rate of 1 pulse per second. more wikipedia
Radio New Zealand broadcasts UTC(MSL) time signals on many of it's stations every hour. They consist of six 'pips' of 1000 Hz tone, at one second intervals, the beginning of each pip marking the exact second. When a pip marks the exact hour, its length is doubled. When a leap second is inserted seven pips are broadcast.
Freeview transmits local time information using DVB-T at least once every 15 seconds with an accuracy of ±2s.
Have a look at http://www.cosc.canterbury.ac.nz/research/reports/TechReps/1999/tr_9901.pdf for a scientific study (from 1999) of the topology of the country's main NTP servers. (A bit dated as GPS is much more widely available now).
See also NTPNotes
3 pages link to NTPServers:
