Nice cheap/FREE roadstop or camping spots North WA??

We are heading North (from Perth to Broome initially) very soon and I'm wondering if anyone has some recomendations of which of the stops on the way up (most likely Great Northern Hwy). We have both done the trip more than once but it has been a few years for both of us and I'd rather have an idea of at least which places NOT to plan a stop at. It'll be a flying trip up no real need for caravan parks just somewhere to stop for a few hours sleep each night. Any suggestions (even good websites) would be appreciated :)

We used the Camps 5 book for our trip from Melbourne to Perth last year. It lists most roadside stops along the way (and cheap caravan parks - $22 per night or under). We got the edition with photos so we could have an idea of what the places looked like. I highly recommend the book! Although I think there is a new edition out - Camps 6.

Best of luck :D