If you want to camp in the coastal region of Olympic National Park, familiarize yourself with the National Park and Indian Reservation regulations. Reservations are required in the summer for the Lake Ozette area. Summer is slightly "greener" and drier, but there are less people & more storms in winter (yes, storms are a "feature" of the coast).
Dungeness Spit is a sand bar extending about 4 miles into the Strait of Juan de Fuca. It is administered as the Dungeness National Wildlife Refuge. Visitors can walk the entire length of the spit on the seaward side (the other side is reserved for wildlife) to a lighthouse at the end.