From Uchronia:
Bradley, James. "The Boys Who Saved Australia, 1942"
Divergence: 1942 CE
What if: Australian troops had not delayed the Japanese march through the Kokoda pass towards Port Moresby.
Gill, John H. "Samurai Down Under: The Japanese Invasion of Australia"
Divergence: 1942 CE
What if: The Japanese turned Coral Sea into a strategic victory by pressing forward its attack and occupation of Port Moresby.
Broderick, Damien. "Schrödinger's Dog"
Summary: Scientists harness bifurcating universes as a result of quantum mechanics. The main character passes through several alternative worlds — one in which whites didn't reach Australia, one from Joanna Russ's The Female Man, one in which Chinese communism has overrun Australia, etc.
Hayden, G. Miki. Pacific Empire
Divergence: 1939 CE
What if: Japan avoided joining in the Tripartite alliance with Germany and Italy, but subsequently attacked the US Pacific Fleet in Hawaii in December 1939, and two days later invaded the Hawaiian islands.
Macintyre, Stuart, and Sean Scalmer (eds.). What If? Australian History as it Might Have Been
Summary: Twelve counterfactual essays on possible turning points in Australian history, including work by Frank Bongiorno, Ann Curthoys, Jim Davidson, Tom Griffiths and Tim Sherratt, Helen Irving, Marilyn Lake, Stuart Macintyre, Peter Read, Tim Rowse, Sean Scalmer, Virginia Spate, and James Walker, plus an introduction by the editors.
Masson, Sophie. The Hand of Glory
Divergence: 1792 CE
What if: The Jacobin takeover didn't happen and the peaceful reformation of French government was allowed to continue. Subsequently, France estblished colonies on the Indian Ocean coast of Australia.
McMullen, Sean. "A Greater Vision"
Divergence: c 40,000 BCE
What if: Aborigines in Australia progressed much much faster, developing steam engines by 22000 BCE, atomic power by 10000 BCE and rockets by 800 BCE.
Summary: Worried by Europe's increasingly speedy and warlike technological progress, aborigines decide to stop Columbus's expedition.
McNaughton, James. New Hokkaido
Divergence: 1941 CE
What if: Japan did not attack Pearl Harbor, and bypassed Australia to conquer New Zealand.
Summary: In 1987, a schoolteacher becomes embroiled in the conflict between the Free New Zealand movement and the Imperial Japanese Army.
Richardson, Hal. "The Time of Fear"
Divergence: 1942 CE
What if: Japan won the Battle of the Coral Sea.
Summary: Life in occupied Australia.
Scott, John A. N
Divergence: 1941 CE
What if: Australia's constitutional crisis of 1941 resulted in a right-wing government.
Summary: A different World War II in Australia, including a Japanese attack on Sydney and occupation of the north.
Vader, John. The Battle of Sydney
Divergence: 1942 CE
What if: The Japanese attacked the American West Coast rather than Midway, and destroyed much of the US Pacific Fleet.
Summary: The subsequent Japanese invasion of Australia.
Voermans, Paul. The Weird Colonial Boy
Summary: A boy follows one of his tropical fish sideways in time to a world in which Australia remains a penal colony in 1978.