We have a good friend in Arcata, CA, and have stayed at Patrick's Point State Park numerous times. We love it! In Redwood country, beautiful agate beach, great walks, old sea stacks and wonderful sunsets, lots of variety, amazing place. It is about 20 miles north of Arcata. Even though you can make reservations, specific campsites cannot be reserved; there are many great spots, though.
http://www.parks.ca.gov/?page_id=417. Not full hook-up sites, so be ready for dry camping.