Bus: The cheapest option, next to hitching. I believe it is also the best way to travel, because it gives you a sense of the overall size of the country. Although flying may be quicker, you miss the experience of what lies in-between. I have found in all my years of travelling that some of my best experiences have come from sitting on a bus for two days. When I travelled Australia back in 96 it wasn't only backpackers on the bus; many Aussies seemed to travel this way.

Greyhound Pioneer Australia:

This is the best option. It has an extensive service which pretty much covers the whole country, and offers great deals such as the Kilometre Pass, Aussie Explorer Pass, or the Aussie Pass. The kilometre pass gives you 12 months to travel the set distance, and you can go where you want, when you want. This is my favourite pass. The Aussie Explorer Pass gives you 6 to 12 months to cover a set route. The downside to this is that you cannot change your plans. The Aussie Pass allows you to travel on a set number of days over a specified period of time. For example you can travel for a total of 7 days in one month. For more information click here to visit their website.

McCafferty's:

The next biggest is McCafferty's out of Brisbane. This service covers the east coast, South Australia and the Northern Territories. Visit website.

Other services:

Firefly: Service between Sydney, Melbourne and Adelaide.

Stateliner: Operates in South Australia.

V/Line: In the state of Victoria, it operates to places where the trains no longer go.

Westrail: Service in Western Australia.

Click here for info on all other bus companies in Australia

Another option is to take one of the backpacker bus tours across the country. These can be an easy way of seeing a lot in a short time, if you are pushed for time. Also, if you are travelling alone then it could be a fun way to meet others.

Here are some links to various bus tours:

Wonderbus

OZ Experience, this seemed the popular one when I was there.

Tours of Australia

Russ's Bus Tours

 

Train: Australia's rail service isn't all that extensive and certainly not the fastest way to get from A to B, but it can be a great way to take long journeys. It will also take you through areas the bus cannot. For example, taking the train from Perth to Sydney, or from Adelaide to Alice Springs will take you through areas of the outback not seen by road. It's also a lot more comfortable than the bus. On the downside though, it will cost more. Here are some useful links.

Australia Rail Passes

Rail Australia

Traintravelling.com

 

Air: The fastest way to get anywhere is to fly. It's not my favourite way of getting around a country because you miss everything in between, but it is convenient if you are limited for time or hate sitting on busses for hours or days, which let's face it is very possible in Australia given the huge distances between places. Internal flights can be quite cheap nowadays. Here are some useful links.

Austravel

Virgin Blue Internal flights Australia

 

Driving: This is another great way to see Australia, especially if you want total freedom to go wherever you want. Buy a car or a camper van when you get over there and sell it when you leave. You often find people advertising the sale of their car or van in hostels when they are due to go back home. Here are some useful links:

Budget rent a car Australia

Australia Car Rentals

Car and Motorhome rentals Australia