Australian passport holders travelling to Turkey after April 10, 2014 will now be required to apply for an electronic visa prior to their arrival in Turkey. Currently the Turkish Government issues visas upon arrival but Australian travellers will now need to complete an e-visa application in advance of their travels.
The cost of the visa is approximately USD$60 per person (subject to change) and visas can be applied for within three months of arrival in Turkey. Online visa applications can be made at iVisa.com.
Obtaining a Turkish Tourist visa online is a simple three-step process which I explain more here.
Details on Australian Passport holders' visa requirements for other destinations can be found in this article.