My friend, Kimberly Powell, has posted a very good article on locating Australian Wills and Estate Records. The following is a teasor from her article posted at about.com:
Wills and probate records can often be a gold mine when researching Australian ancestors. Wills generally list surviving heirs by name, providing confirmation of family relationships. Probate records which document the handling of the estate through the court, whether the deceased died testate (with a will) or intestate (without a will), may help identify where family members were living at the time, including those residing in other Australian states, or even back in Great Britain. For more information on the valuable genealogical clues estate records can provide, see Probing into Probate Records.
There is no central archive of wills in Australia. Instead, wills and probate registers are maintained by each Australian state, generally through the probate registry or probate office of the Supreme Court. Some states have transferred their early wills and probates, or provided copies, to the State Archives or Public Record Office. Many Australian probate records have also been filmed by the Family History Library, but some of these films are not permitted to be circulated to Family History Centers.