There is a pool of servers at nz.pool.ntp.org, which provides RoundRobin DNS access to publicly accessible NTP servers that have agreed to be part of the pool.
Many ISPs have NTP servers for their customers:
or you could try querying your ISP's DNS servers with ntp or ntp1.
Some universities have publicly accessible servers:
For a long time WaikatoUniversity had public NTP servers. They are still available but no longer publicly accessible.
pool.ntp.org has NTP server pools for many countries.
List of public German NTP servers.
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. (But GPS is much more widely available now.)
3 pages link to NTPServers:
