Welcome to FT, OhCanada. I am also always on the lookout for cheap flights to Oz. Others on this board have advised me to check
www.jetsettravel.ca as they offer some great fares, including those on *Alliance carriers.
I usually travel to MEL in late Feb-early March and have certainly been able to find good fares the last few years on AC or UA.

Good luck. I'll let you know if I hear of anything.
H