Camps Australia Wide is a good source of information for camping (you can also get a copy of the gps locations to add into your gps). On the long distance runs I normally use the covered picnic tables in the roadside parking bays well outside of towns.
+1 on the Camps Australia Wide and it has a permanent place at the bottom of my Tank Bag.
+1 on the side of the road and theirs a ring and watch of mine under a picnic table half way between Narooma and Batemans Bay. Have a 3x2 meter tarp on board that you can put over the table in case it rains
Hint: get used to using Google maps
Find the side of the road you want to stop at in the Camps Australia Wide and then on Google maps.
Put that little yellow bloke, that's up on the top left on the spot and take a look around.
And guess what. You've just saved yourself $20 if you had stopped at a caravan park, $60 if you had stopped at a Pub or a $100+ if you had stopped at a Motel
When its been pissin down rain the toilet blocks at them wayside stops and the Bus shelters
on the side of the road are most excellent
Last Hint. Try to stop with a full tank of petrol. Just a hell of a lot easier heading off in the morning without having to stop a few kays up the road. That way your first stop can be a couple of hundred kays up the road for breakfast