Boat
There are plenty of opportunities in Australia to hop on a yacht cruise on to your next destination. Places like Cairns and Airlie Beach with a large amount of boats are great spots to look for potential rides.

Notice boards in hostels, backpacker travel agencies, and internet cafes will generally have a few ads looking for crew to help the capatain sail and share costs. The deal is usually food and a place on the boat in exchange for a bit of help sailing, cooking, cleaning and usually a daily fee. I think I paid about $35 per day. Considering that included food, accommodation and transport, it was a pretty good deal. At the time, most of the ads I saw were asking for over $45.

Popular routes from Cairns include down the coast to Townsville, The Whitsundays, and Airlie Beach. Some ads were looking for people to go out just for a few days for a BBQ and drinks before returning back to Cairns. Some boats even go north to Port Douglas or even around Cape York all the way to Darwin. I've also heard of boats making international trips to New Zealand and north to Asia. I even met a guy who was due to sail from Perth to Sydney taking three weeks to get there.