We love this book - 2500 free or cheap campsites in Australia - and it's always in the car, but a website that looks handy is aussiecamping.
There are more campsites listed from Queensland than other states at the moment but it is user-driven so that might change over time. It may be a useful tool to plan your next trip. Note that their forum seems to have been spammed recently. I suppose they'll tidy it up soon.
