Good hunting.
A very good general search engine is Google. It searches on text-strings rather than on index entries, and can trawl up thousands of hits on subjects that index-based search engines simply miss. To search on Google, click here.
Within this site, there are some searchable references listed on the Links page. Click on the "Links" button in the panel at left (it's the button at the very bottom) and flip through the list.
If you are looking for a specific ship, but cannot find it on this site nor in one of the references on my "Links" page, there may be many reasons. If the ship you want was not commissioned into the Royal Australian Navy, you won't find it on this site. In this case your next step would be to try the civil shipping register. Click here to search the National Archives of Australia site, where shipping registers from days gone by can be perused on-line.
If you want to find information about a specific serviceman or woman, then click here to search the National Archives of Australia Family History page. This page has a very useable search function sorted by period.
If you're looking for details of battles, skirmishes or oral history, there are many web-sites devoted to Veterans' Associations, and they can usually be found by searching in Google for some combination of key-words such as veterans, "world war two", associations, "south west pacific", "Australian Navy".... and so on. To search on Google, click here. "Bob York's Royal Australian Navy" site, and "The Gun Plot", both on my "Links" page, are two Australian sites that can get you in touch with Australian veterans.
If you're looking for a specific place such as a harbour, island or stretch of ocean, you need to explore gazeteers. A website which provides access to a searchable on-line gazeteer is at "The World Gazeteer"; but the more obscure the place you seek, the more likely it is that you'll have to visit a big library in your home town and use their hard-copy edition. The entire South West Pacific was surveyed during world war II, and the results of these surveys were all collated by the US Navy Hydrographical Service; even the most obscure cape, bay or lagoon is named somewhere in this vast work, but I've never been able to find it on-line.
If you have some general inquiry that doesn't fit any of the above, there are two more places you might try. One is the "Ship Ahoy" web-ring, which is collecting sites like this, and of which this site is a member. And if all else fails, try e-mailing me by clicking here.
Once again, good luck with your research.