Lawdy, I know this is gonna degenerate real fast, but to answer your question. There are three legally approved nude beaches in Sydney: Lady Bay, Obelisk, Cobblers. The most famous (and first), Reef Beach, has now banned nudity.
Australians in general aren't big fans of public nudity, preferring to keep such action firmly linked with sporting events and the overuse of alcohol. There will, however, be an event Disrobe to Disarm, at Byron Bay on the weekend
Disrobe to Disarm where Grace Knight and some locals will be getting their kit off to protest the possible war with Iraq. It's worth a try I say!