Kakadu national park a great mix of all: nice scenery, hiking opportunities, animals and rock paintings
Mereenie loop road This road links the recommended MacDonnell ranges with the Kings Canon. A permit is required which you can get in Alice Springs.
Ayers rock Not to be missed. But please respect the Aboriginal wish and don't climb it.
Olgas Good hiking oportunities in moonlike landscape.
Grampiens national park tame Kangaroos
Great Ocean Road spectaclar rock formations
Phillip island Don't miss the penguin parade
Sydney one of the most pleasant cities that we have visited

Camping Australia has a good infrastructure for camping. If you continue to New Zealand, try to rent Campers at the same company to get a reduction (for example Brits)

flies In the outback you will only be able to use one hand, the other will constantly fight the flies. Or do you really want to wear that silly hat with a net? Did I tell you that they bite ?
wine For those who like wine, don't miss the Barossa valley where you can go wine tasting.
Aborigines If you are interested in their culture, you best go to the north or center of the country.