www.abr.gov.au (for applying for an ABN – Australian Business Number)
[Since 28 May 2012, in order to register a business name in Australia, the person, company or 'entity' proposing to trade under the business name, must first have an ABN (or an ABN application reference number).
An ABN may be applied for, at no cost, through the www.abr.gov.au website run by the Australian Taxation Office.]
[You might want to use the above resource for - for example - checking to see if a proposed business name you are looking to register as a business name has already been registered as a trademark, or for applying yourself to register the business name as a trademark.]
Incorporator.com.au (for incorporating a company)