Dictionary of Australian Slang: www.australiatravelsearch.com.au/trc/slang.html

Sampling below:

Arvo - afternoon.
Av-a-go-yer-mug - a phrase used to encourage someone to put more effort into something.
Barney - an argument, fight.
Big smoke - the city.
Billabong - a waterhole.
Cobber - a mate, friend.
Corker - something striking or astonishing; something very good of its kind.
Dinkum / dinki-di - true, honest, genuine.
Earbash - to talk incessantly, someone who talks too much.
G'day, gidday - a greeting meaning good day.
Get stuffed - go away.
Grog / booze - alcohol. beer, spirits.
Grommet - an idiot; a young surfer
Hooroo - goodbye.
Joe Blake - snake (rhyming slang).
On ya mate - usually means well done but often used sarcastically.
Open slather - free-for-all, anything goes.
Oz - Australia.
Scrub up - dress up.
Servo - a petrol / service / gas station.
Sheila - girl, woman.
Spit the dummy - get very upset about something.
Sunnies - a pair of sunglasses.
Ta / tar - thanks.
Tucker - food.
Walloper - one who thrashes someone.
Wally - someone who keeps making mistakes.
Wombat - a simple minded person.
Yonks - a long period of time.