This spider was found on my Vegetable garden fence last Wednesday evening. It is, I believe, Eriophora pustulosa, the Garden Orb Weaver. The species is very variable in colour and pattern as it takes on the colour of it's surrounding. It ranges from yellowish right through to black.
The USQ's Find a Spider site says, the "presence of two projections (tubercles) on the front upper surfaces of the abdomen and a row of three near its pointed end are characteristic of this species." These can be seen best in photo #1. Below the three posterior tubercles are another two vertically aligned tubercles so if you were to view it from behind all five projections would form a letter T. (see diagram #5) It also has a dark quadrilateral area on the ventral surface which is surrounded by a white margin as can be seen in photo #4.
Female body length is 7 - 15mm and males 7 - 8 mm.
Note: older texts refer to this species as Acroaspis tuberculifera or Araneus pustulosus
Hickman V.V. - 1967 - Some Common Spiders of Tasmania - Tasmanian Museum and Art Gallery.
University of Queensland Find a Spider Guide - http://www.usq.edu.au/spider/find/spiders/612.htm