Rolf Harris WAS born in Australia. Whether he counts as having contributed much to the world or not, I don't know.
On the other hand, Nicole Kidman, Olivia Newton John, the lead singer of Men at Work (Colin Hay) and all of the Bee Gees were NOT born in Australia. I'd still count all of them as Australian, because thats where they got their starts in their respective careers.
While we're in the entertainment field, another famous Australian actor is Errol Flynn.