I buy most of my pet supplies now from http://www.worldforpets.com.au/
All of the profits go towards the RSPCA, and their prices are much cheaper than regular pet stores.
The postage is really cheap too (it cost me around $5 to get a few packets of all wormers, a brush and some flea stuff sent to my house).
I find BigW now has a really great pet section as well. So I also often buy toys etc. from there.