Here is a list I've compiled of Aussie slang I noticed while in Australia, as well as some funny and/or interesting little tidbits about their culture. (To all my Aussie friends: please feel free to add to this list even thru comments! :))

Oz-Australia
G'day Mate!-Sums up Aussie culture right here - this is their greeting
Aussie-Australian
Maccas-McDonald's
She'll be right, mate!-It'll be okay
No worries
Thongs-Flip flops (the older lady I sat next to in the plane on the way there said, "Did you bring thongs?" And I was really shocked she would ask me such a personal question!...then I realized she was talking about flip flops. :))
Amah!-Oh no!
Dag-You silly goose. (Literally: You piece of crap on a sheep's bum! Sarah, this one's for you ;))
Far out!-Crazy! No way!
Rallying-driving cars madly on dirt fields, instead of doing doughnuts on snowy parking lots
Brekky-Breakfast
Sheila-Girl
Bloke-Guy
Bogen-Lower income/intelligence
Barbie-BBQ
Mucking around-Messing around/goofing off/joking around
Ay/hey?-Put it at the end of sentences, ex: That was pretty sweet, hey?
Swagman/swaggy-Like a hoboe, only it's a good thing, an expression of the Aussie bushman kinda
Just a tic-Just a sec
Ta-Thanks
Good on ya- Good for you
Jumper-Sweater/jacket
Bonnet-Hood of a car
Boot-Trunk of a car
Mozzies-Mosquitos
Arvo-Afternoon
Cuppa-Cup of tea
Tele (pronounced Tell-ee)-TV
Uni-College/university
On college-Dorms at uni
Whinging (pronounced Win-jing)-Whining/complaining
Rooting-Just don't use it!!
Have a go-Try it
Bludger-Lazy bum
Alco-Alcoholic
Unco-Uncoordinated
Yabo-Redneck
Platting-Braiding
Braiding-French braiding
Savory-Salty
Trekking-Hiking
Trekkies-Track suit
Swimmers-Bathing suit
Ginga-Red head
Chutney-Fruit-based (tomato or pineapple), savory, to put on scones or roast beef, like a relish consistency
Chips-Fries
Duna-Cover/blanket
I reckon
Stuff!-Shut up! No way! Crazy!
Brizzy-Brisbane (the name of a city there)
^Yes, I truly heard all the above words used there regularly.

If someone asks you over for tea, it means dinner. So don't eat before you go.

Their bathrooms have a shower/bathtup and a sink... then they have a separate room with just the toilet in it. Weird! And they're not always rooms directly next to each other! And instead of saying "I need to use the restroom," it's perfectly polite to say "I'm going to the toilet."

It's a much more laid-back culture. I could call my professors by their first names!

Hog's Breath Cafe-A restaurant chain there that we loved

Their public schools have uniforms and the kids take public transportation instead of school buses.

Didgeridoo- (did I spell it right? a long wooden instrument you blow through that sounds like your stomach rumbling - played/created I believe by the Aboriginals, the native inhabitants of Australia...and don't ever call them Abos - I figured that's what they'd be called since Aussies shorten everything... but no, that's offensive)

Their clubs play a lot of techno music, which is really hard to dance to after the first couple songs. And the Aussie guys we saw danced CRAZY! They flailed their arms EVERYWHERE.

There are a lot of Aussie vs. Kiwi (new zealanders) rivalry - kinda like the US and Canada, but way more hardcore ;)

Aussie humor: very very sarcastic

Some big Aussie sports:
Netball (like basketball, but you can't dribble/move with the ball), Cricket, Rugby

Some expressions:
Sweet as! Fully! Heaps (lots)!

Some Aussie foods:
VeggieMite (nasty nast!), TimTams (amazing chocolates!), Pavlova (like a cake made out of meringue), Lemingtons (little sponge cakes covered in chocolate and coconut, incredible)... they also have lots of huge blocks of cadburry chocolate that is incredible-and when they have get togethers, people bring blocks of chocolate instead of chips. And I mean, these blocks of chocolate are huge!! mmmmm a girls dream ;)

Some famous Aussies:
Carl Barron-Comedian; Missy Higgins-Singer; Jamie Oliver and Margaret Fulton-Have good Aussie cookbooks

The Band O'Coots is an awesome Aussie bush dance band - they play the music and teach you how to dance. It reminds me of Irish square dancing.

They drive on the wrong side (left side) of the road, and their passenger sits on the left while the driver sits on the right. Most of their intersections use circles with yield signs (where you yield to the person coming from the Right), instead of using four-way stops.

Their toilets have two buttons - one you flush when you go #2 (gives more water and a much longer flush) and the other button is for when you go #1. I didn't know that for the first couple months. I'd just alternate buttons.

Australia is in a ten-year drought and Toowoomba, where I was, is supposedly about to run out of water in the next year or two.

An Aussie pickup line: "If you want a hot date (bum), sit on the bonnet (hood) of my car!"