Markets are probably the cheapest shopping alternative in Australia. You'll find one almost every weekend; anywhere you are in the country. Weekend markets are where you'll learn a bit about the local area and find some of the most “Australian” things around. Most major cities have a big weekend market in a fairly central location including: 

Sydney

Paddy's Market Haymarket, central Sydney

opens Wednesday-Sunday

Paddy's Market Flemington, west Sydney

opens Friday-Sunday

Chinatown Night Market

opens Friday

Glebe Markets

opens Saturday

Paddington Markets

opens Saturday

Farmers' Market, Pyrmont

opens every 4th Saturday of the month

The Rocks Weekend Market 

opens Saturday-Sunday

Leichardt Organic Farmers Market, Rozelle

opens Saturday

Artisans' Arts & Craft Market, Darlington

opens 1st Sunday of the month

Bondi Beach Market

opens Sunday

Newtown Designer's Market

opens 3rd Sunday of the month

Rozelle Markets

opens Saturday-Sunday

Balmain Market

opens Saturday (except the 1st Saturday in January)

Kiribilli General Markets

open the fourth Saturday of the month January to November, the first and third Saturdays of December - more info

Melbourne

Queen Victoria Markets

opens Tuesday & Thursday-Sunday

Adelaide

Central Market

opens Tuesday, Thursday, Friday and Saturday

Darwin

Mindil Beach Markets

opens Thursday and Sunday

Fremantle

Fremantle Markets

opens Friday-Sunday

Hobart

Salamanca Market

opens Saturday