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.
Hi My local Pet shop, Pets Unleashed in Morningside actually re-homes cats for the Animal Welfare League. They do sell some other pets such as guinea pigs, hand raided birds, fish but do not sell puppies. The pets always look happy and well cared for.