Australia-wide legislation: the Australasian Legal Information Institute or perhaps "Lawlex" are good.  The "Scaleplus" site also has State and territorial legislation. Findlaw is an all-purpose information centre for legal advice, finding lawyers, legislation and case reports.

Victorian laws led the way for much of Australia's OH&S reforming legislation.  This site has useful links to legislation, Codes and related material.

New South Wales: the NSW Law and Justice Foundation (which also has links to most other main databases, plus some judgements).
West Australian-based legislation and information ( includes links to other jurisdictions)
Queensland:  legislation, advisory Codes, etc
South Australian OH&S laws
Northern Territory legislation

Commonwealth OH&S Legislation and guidance material

Standards Australia - includes abstracts of most standards
International Standards Organization (ISO)

State WorkCover or equivalent Authorities:

NSW: www.workcover.nsw.gov.au
VIC: www.workcover.vic.gov.au
ACT: www.workcover.act.gov.au
TAS: www.wst.tas.gov.au/node/wstlegislati.htm
SA: www.workcover.sa.gov.au
WA: www.workcover.wa.gov.au
Northern Territory Work Health Authority
Queensland Department of Industrial Relations, Workplace Health and Safety: 
Tasmania Workplace Standards: 
COMCARE (Commonwealth Government)

National Authorities:
NOHSC (National Occupational Health and Safety Commission)
NIOSH (in the USA)
NIH (in the USA)