I am an Indian citizen and passport holder. I am currently on a visitor visa in Melbourne, Australia and my visa is valid for next 2 months. Is it possible for me to apply for US B1/B2 visa from here, or do I need to be in India only to apply for it?
You can apply in Australia. If you do, though, the risk that you'll lose your $160 application fee to a rejection is somewhat higher:
Q: Can I apply for a visa in Australia if I am not an Australian passport holder or a permanent resident here?
A: An applicant has the right to apply for a nonimmigrant visa at any U.S. consulate abroad, therefore you can apply at any U.S. consulate in Australia.
However, it may be harder to qualify for a visa when applying outside your own country of permanent residence. At your interview you will be required to demonstrate that you have strong ties abroad, and that you will return overseas after your visit to the U.S. If you choose to apply in Australia, keep in mind that your application may be refused, and the application fee is non-refundable.