National Parks information
National Parks in Australia are administered by the State in which the park is located. For this reason, there does not appear to be any official central point for National Parks information, nor any national passes for entry to parks or camping in parks.
Many National Parks have no entry fee, but those that allow camping usually charge a camping fee. Some States sell an annual entry pass to the parks within them, or an annual camping pass, or a "holiday" pass for up to two months, or variations on these passes. Some of the Web sites listed here give the type and cost of the passes available; others don't. In some cases you can order and pay for your pass online.
New South Wales - National Parks and Wildlife Service http://www.nationalparks.nsw.gov.au/ -- look for the link to annual passes and other fees
Western Australia - CALM = Dept of Conservation and Land Management
A detailed site, with maps, opening hours, facilities, tours, all you need to know. For passes, go directly to: http://www.calm.wa.gov.au/national_parks/park_passes.html
Queensland - Department of Environment and Heritage
Has information on each park but only general info on camping fees and nothing that I could find about entrance fees (maybe there aren't any?) or passes.
Department for Environment, Heritage and Aboriginal Affairs
Good maps, searching, lists of facilities and fees, etc, including passes good for various combinations of time and parks in SA.
Northern Territory - Parks and Wildlife Commission
http://www.nt.gov.au/ipe/pwcnt/index.cfm - hidden under "About Us"
Victoria - Parks Victoria
Map, list of facilities, lots of info.
Tasmania - Parks and Wildlife Service Visitor's Guide
Fees and park passes on this page:
Can order passes online.
A related private site, http://www.geoffmurray.com/, has beautiful photos of scenes in Tasmanian national parks.
ACT - Environment and Heritage
Australian Alps National Parks