Which part of the coast?
I grew up on the southern coast.
Just south of the OR/CA boarder on Smith River is Jedediah SP which is just off the coast in a redwood grove.
Head north on 101 and there is a nice little hike in tent camp right on the beach, can't remember the name of that one.
Continue north and take a right up the Chetco River, there is a great campground right on the river.
Just north of Brookings is Harris State Beach Camp ground. A little north there is a private campground called Whales head, more oriented to RV's but they have nice facilities and private access under 101 to the beach. Clean showers and a laundry room, the resturant serves some fantastic seafood but it's more old school, heavy on fried stuff. I swear they put about 1/2 pound of bacon in every serving of green beans.
North of Gold Beach there is a neat campground called Humbug mountain. Don't miss the Prehistoric Gardens located nearby. I went there on field trips back in the 60's and it's still cool.
Around the Port Orford area there are places to primitive camp along the Elk River.
Based on growing up on the coast I prefer to camp inland a couple of miles, it's much more comfortable. The beach is either windy or damp or both.