This link goes to some practice questions – scroll down to the relevant section.
Here are some links to an American maths competition that is quite similar to the Australian Maths Comp. These questions are most useful for Year 7 and 8 students: 2012 competition 2011 competition 2010 competition
Here is one for Year 9 and 10 students: 2013 competition
…and for VCE students: 2013 competition (These are pretty challenging!)