There are several free campsites, but may be not be open when you arrive. They are first-come/first served, one on the Sol Duc(Tumbling Rapids)is closed right now. The Hoh has two or three more. Sol Duc Hot Springs is a great place to stay because of the water! There are National Park and State Campgrounds on each river, check the websites, some will take reservations. Have fun, and release all the wild fish!