In angus & robertson bookstore, I found a Boiling billy publication called Camping guide to New South Wales..
I absolutly LOVE IT!!! definitly one of the best books I've bought. It lists over 650 campsites, costs and phone numbers to get permits and local autorities. It also lists roadway rest stops and has a comprehensive touring map. The book is split into sections, eg.Close to Sydney, Hunter region, far south coast, central coast the outback etc. and covers National and state parks, forrests and reserves.
It's great, just look up the region you want to go to and pick a site, It has instructions on how to get there and also picks the top 5 campsites so you don't have to second guess yourself. It also lists alot of free campsites and amenaties too.
It cost me about $30, but really well worth it.
The most expensive site listed is $30 and that's smack bang in the middle of Sydney Harbour. dingaling Island. My Girlfriend wants to go there, but I believe camping is all about getting away from the big smoke.