Australian consultancies are a bit fragmented. However, some large ones tend to dominate: Accenture, IBM , EDS etc...
Also, indian consultancies such as Infy and TCS also have a big presence there.
All of the above are generally bodyshoppers - all bill you at monster $ to the client, pay you a very small portion of the bill, make you work 24hrs, and are rife with office politics which make it difficult to work your way up the ladder. Thus, these are not the kind of places you want to be in.
I would suggest some of the mid sized aust consultancies such as Oakton and SMS Mgt and Tech. They pay good, treat they employees really well and are full of bright fun people...the kind of environment you want to be in.
One word of caution: Australia ( especially sydney) is extremely expensive- the rent, cost of living ( everything from a coffee to a car) means that your salary in sydney better be in the 6 figures. Dont accept anything under this threshhold.