The Local Taphouse in Darlinghurst updates their on-tap beers constantly and do a lot of beers from smaller breweries, so that place is pretty awesome
Also you really can't go wrong with the Redoak on Clarence Street too. They switch up their beers fairly regularly and you can get a decent meal there too
The Heritage Bar in the rocks is wonderful for a meal and some on tap foreign German beer. I have been there twice now. Don't forget to take a look at the colonial footings of the building through the glass floor as you enter. Magic!