If you are going to Sydney you must go down to the Rocks on the
weekend. Its one of the best art and craft market, also all the
shops in the area are crafty. Just do not buy opals there. A rule in
Sydney is, never buy opal from a shop where the prizes are displayed
in Japanese yen as well.
On Circle Quay you will find some galleries as well. It worth the
walk down by the water there anyway.
If you are hoping to find cheap opals, you can, but be prepared to
drive down to Lighting Ridge. You can buy good black opal for the
fraction of the price. Its a cool little town with not much but dirt,
dust and lots of opal. If you want I can give you some contacts for
Opals on the Gold Coast as well Which is about an hours drive from
Brisbane. (thats where I live).
Its so much to do at both cities, and if you want anything specific,
let me know.
And if you are driving from Sydney to Brisbane, you will find plenty
of bee keepers as well.