Depends on what type of work you're after.
Practically all picking, packing and low paid hospitality jobs are now done by backpackers. If you have a trade it's a lot easier.
I've tried all the government and non government associations over the years and it gets down to being where the work is when it's available.
There is a huge well organised network that foreign workers have set up , mainly social media and word of mouth. By the time the average Aussie gets around to applying for a job the local backpacker hostel has arranged to drop 20 workers at the gate or pub or cafe free of charge and the employer can take his pick. They'll work for peanuts, no super paid and being foreigners they have no idea what conditions are legal and what's not.

Don't know if it's still the case but in 1997 when I did some picking at Bowen the foreigners were buying and selling tax file numbers and identities for about $150.
I wouldn't pay 1 cent to an employment agency, present yourself with the necessary qualifications and you'll do just as well.

I was told in '95 by the CES [ Commonwealth Employment Service] that spending money on fuel and travelling to areas like the Kimberleys where the is a demand for labour between May and October could turn out to be a waste of time and money.
They were correct, I got there and found hundreds of backpackers had every job in the above fields. I finished up going back to my trade as a mechanic to get work.

Also there is a huge number of New Zealanders now soaking up jobs in Australia, an item on the net yesterday states that 25% of full time jobs have been taken by people born overseas.
Best of luck in your search.

http://www.noboundaries.com.au/positions%20vac/Emloyment.htm

 

http://www.qorf.org.au/_dbase_upl/3.%20eKit.pdf

Gertie, the caravan ekit in a beauty, and leads to a lot of interesting sites. Thanks, Bill