Australia offers a variety of excellent wine experiences. For general information on wines and wineries, refer to Australia.com. The South Australia website has a particular focus on its top five wine regions, namely Barossa, McLaren Vale, Clare Valley, Coonawarra and Adelaide Hills.
The easiest way to find a wine tour in Australia is to look up day tours in TripAdvisor for the particular city you are based in. For example, I took a McLaren Vale tour out of Adelaide (Barossa was another option) and a Yarra Valley, Victoria tour out of Melbourne.