Wikicamps would have to be the best at this point in time, think it still only costs under $10
Doesn't need an internet connection to function you just need to download the database for States you will be travelling in, before you leave home and update occasionally when on free Wi FI. It is being updated by users constantly, so is always fairly up to date.
Cheers
David

if youre reasonably ok with setting up apps and simple programmes, wiki is the way to go. If youre not pc savvy at all, then get one of your kids or grandkids to do it for you. If you don't set it up correctly, you will not get all the parks, low cost and free camp sites and what features they have as well as other points of interest.

I didn't have problems, but when we were on the road last year, helped 2-3 other nomads who couldn't get it to work as they wanted, simply because they were pc "scared".

Also keep in mind that many sites are not confirmed. Make sure there are a few comments for a site and the bulk of those are positive (you will always get a few knockers) to confirm the site actually exists. We travelled through SA, VIC and NSW as well as the lower part of our home state, WA, and there were sites showing on the state maps with no comments, prices or photos - usually these sites don't exist and have been created by people who have entered in incorrect data or co-ordinates.

Otherwise wiki is great - is cost me $7.99 when I last paid about a year ago. Real value for money and the two brothers who run the site are very helpful if you get stuck in trying to get the programme to run or whatever - they will answer your question pretty promptly

Caravancaravan is very good also. Yes it is spelt that way. I also find it easy to use.