I absolutely love Pizza Tutti's in Northbridge for gluten free pizza. Their bases are so good it's hard to believe they are gluten free, and they are knowledgeable about what toppings do or do not contain gluten. The flavours are just spectacular as well. I wrote about them over on Sydney Fun if anyone is interested.
Crust does great gluten free pizza. I love the peri peri chicken one! It is pretty reasonably priced when too.
Also there used to be a restaurant in Newtown called Basil that did amazing gluten free pizza's. Not sure if it still there though...