Sadie Creek Campground west of Joyce on Highway 112 is perfect for a certain group of people, and not so amazing for another group of people.
If you enjoy Off-Roading or motorized anything this is the spot for you! With six spaces and plenty of parking for your trailer or RV, Sadie Creek has everything you could ask for. Also an extensive system of trails both on the northern and southern end of the highway will give days of riding through heavily wooded (and probably difficult) terrain. Also a great place for equestrians although if your horse spooks easily perhaps not.
If you are a tent camper or enjoy solitude as apposed to the social aspects to the great outdoors I would heavily advise against this campground. It's ok for a quick night's stay if a spot is open but the sites are practically right next to each other and expect to share the space with others that may not be so quiet. I would suggest Lyre River campground 6 miles to the east if that's what you're after.
Although there's no hook-ups there is a pit toilet on site. With a yearly Discovery Pass ($30) the campground is free. You have Murdock Beach down the road which gives great views of the Salish Sea. Closest town would be Joyce 10 miles to the east, with a great general store and through street to Lake Crescent. Multi-use trails run out from the north or south of the campground so great jump-off point for hiking or trail running in the Olympic National Forest.