Olympic National Park on the Olympic Peninsula in Washington can easily be divided into three distinct ecosystems: Mountains, Coast, Rainforest. This post focuses on the coast.
The Park: The main section of Olympic National Park contains the glaciated peaks, temperates rainforest, and lowland ecosystems of the Olympic Mountains. However, if you venture west of this area, across Hwy 101, you'll discover a very different view of the park - the soaring seastacks, colossal driftwoods, and stoney tidepools of the Pacific coast. Depending on how much time you have to spend, you can check out everything from the ancient petroglyphs at Wedding Rocks to the arches at Rialto Beach. Take some time to beach hop up and down the highway from Ruby Beach to South Beach with the creatively named beaches 1, 2, 3, & 4 in between. And if you really want to spend some time on the Washington coast, take the 73 mile Wilderness Coast Trail along the "Wildest Coast in the Lower 48" for a chance to see seashore completely inaccessible by car.
Camping: South Beach - The largest and most popular campground along the Olympic Coast is Kalaloch, but if you go just a few miles further south, you'll come to the much smaller South Beach campground. South Beach is the only drive-in campground right on the beach (at Shi-Shi campground, which is supposed to be unbelievable, you can pay to park on the reservation and hike-in to the site, but can't actually drive-in). Being able to go to sleep to the sound of the waves and the smell of the sea is worth getting there early to secure a prime spot with an ocean view. I arrived about 11 AM on a weekday and got the last beachfront site, so plan ahead. Also be aware that this campground offers no privacy between sites and is dominated by RV's, but it's the price you have to pay if you don't have time or the desire to hike down the beach to a nice spot.
Hiking: Rialto Beachwalk - Just outside of La Push, this 3-mile roundtrip beachwalk takes you alongside some of the most striking seastacks in the park. Start at the main parking lot at Rialto Beach and head north. The further you walk, the thinner the crowds get, but you'll have giant bleached driftwood to keep you company along the way. After about a mile and a half, you'll end up at Hole-in-the-Wall, a natural arch. Get there at low tide to be able to explore the arch and the starfish and anemone filled tide pools throughout the area. I would caution going too far north of the arch because if you misjudge the tides, you could easily get trapped on the wrong side and have to wait out the entire tide cycle to return to you're car.
Pit Stops: Forks - Any Twilight fans out there? Forks is a must stop for you. The setting for the famous vampire novels has thrown itself whole heartedly into the Twilight universe. Visit Edward Cullen's and Bella Swan's homes, find safety in "wolf country" on the Quileute Reservation, and take in the many vampire and werewolf puns adorning every other business in town.