The Railway Archives has a large collection of maps and diagrams of the railways in Australia, both current and historical. A selection is available here.

Current Maps
New South Wales

Sydney
Victoria
Melbourne
Queensland
Brisbane
South Australia
Adelaide
Tasmania
Hobart
Western Australia
Perth

Historic Railway Maps
Australia
Aust 1940
New South Wales
Digest NSW
NSW diagram map
Queensland
queensland 1968
Victoria
Victoria Map 1932
VR_Suburban_map_1965
Western Australia
WAGR 1939
Tasmania
tas
South Australia
South Australia Map 1937