You could go to Chadstone..was just there recently and due to spring carnival coming up, every shop had lots of pretty dresses, matching shoes and accessories. There were stores in Chadstone that I had never heard of.
I am a huge Alannah Hill fan!! Leona Edmiston is another one, although I like Alannah for her different style.
Seed women had some great dresses. Review usally have nice dresses.
You could also try Kookai or Dejcuba, they have some funky things as well.