The holder of a New Zealand driver's licence will generally be allowed to drive in Australia without having to obtain an International driver's licence. However as each state in Australia have slightly different rules towards international drivers and slightly different road rules, it is very important to check with the licencing agency in the particular state that you are planning on visiting. See the list below:
New South Wales: www.rta.nsw.gov.au
Victoria: www.vicroads.vic.gov.au
Queensland: http://www.tmr.qld.gov.au/
South Australia: www.transport.sa.gov.au
Western Australia: www.dpi.wa.gov.au
Tasmania: www.transport.tas.gov.au
Northern Territory: http://www.transport.nt.gov.au/
ACT: www.canberraconnect.act.gov.au