The Society of Australian Genealogists (SAG): www.sag.org.au is an excellent genealogical organization. However, why would people outside of Australia even care?
Often in our research we plow through records only to see “Ireland” as the place of birth. Now consider this. In the nineteenth century, most immigrants had a relative who went to Australia, either as a convict or free. So to identify that ancestor, and begin using the Australian records is to open up an extra avenue from which to explore the question of Irish origins.
Sometimes I find it quicker to contact the SAG for the name of a genealogist for help rather than plowing through rolls of microfilm at the Family History Library. I’ve had the pleasure of working with many of them in the past. Like they have told me, it is common for the name of a county, parish and even townland in Ireland to be preserved in their records. This makes your Australian branch of the family very important.
The SAG members publish books and create databases. The SAG Library in Sydney has family histories and biographies, local and school histories, vital records indexes (civil registration), shipping records, probate collections, cemetery transcripts and burial registers, various commercial databases and indexes. Also at the SAG Library is a growing manuscript collection of more than 28,000 files. Within the files are family papers, pedigrees, photographs, certificates and research notes. Their quarterly journal Descent is recognized internationally for its quality.
From my personal experience, if you have a lost Australian branch, I would highly recommend contacting the SAG. They have a special Irish Interest Group: http://irelandhome.com.au