Below I've listed a number of auction houses in no particular order. Remember to practice your confident bidding voice and whatever you do, don't scratch that itchy nose.
The venerable Bonhams and Goodman has auction sites in Waterloo and Double Bay and is one of Australia's largest auction houses selling fine goods such as collectible cars, jewellery, art, furniture, and more. Check out there upcoming auctions here.
D&D Auctions are located in Alexandria and concentrate on new furniture and whitegoods. Auctions are held each Sunday at 11am.
Laws is a good place to pick up goods for the home such as sofas, whitegoods, stoves, cupboards, etc. Located in Wetherill Park they have regular weekend auctions but most are during the week.
Raffan Kelaher and Thomas can be found in Leichhardt and have regular auctions of bric-a-brac, art, whitegoods, and furniture. View on a Saturday and leave a bid.