There are two options now: You can get a 30 day Indian tourist visa on arrival. This visa is available now for most foreign Nationals. It is single entry only, and can only be obtained arriving at an international airport in India. It cannot be extended beyond the 30 days. Cost is the INR (Indian Rupee) equivalent of US$60. For more information or to apply go to: www.indianvisaonline.gov.in/visa/tvoa.html.
The second option is obtaining a 180 day Indian tourist visa in advance, which saves a lot of time clearing immigration at the airport. However it means filling in forms and sending away your passport. This visa can be single or multiple entry, and costs a little over A$100. (US$70) For more information or to apply go to: www.vfsglobal.com/india/australia.