The "Whereis" website provides online maps for most major cities & towns across all states & territories of Australia.

"UBD" Universal Business Directory is the #1 street directory across Australia.

Street-directory is excellent for Australian capital cities (best for Melbourne) -- and also New Zealand. It has a far superior interface -- when you zoom in, you can just click/drag to move around to neighbourning maps/pages -- no awkward, slow links to click on to see nearby locations not visible. Once you get used to it, it's quicker and simpler than other sites.

Also, street-directory gives you map references for popular Ausway (Melway, Sydway, Brisway etc) map directories -- centre the location, click one of the zoom levels and it tells you the map page/grid information -- great to refer to if you need to use the directory (not UBD though, that's a different publisher).