if youre coming from the north, Humbug mtn state park in northern oregon(its on the coast about 30 miles from ca. i think) has hot showers. Super cool! and its beautiful. Once you get down in the redwoods park, the campsites abound. south of the redwoods park, but north of arcada, is clam beach, which is a good place to sleep.
I was over that way for a holiday years ago, I remember going to Yosamite park. A truly cosmic experience, in every sense! the Sequoia tress were magical, the soft bark feels warm and it's as though there's a heart beating inside causing a feedback resonation with your own body. I think it's no too far from the Redwood area (but I'm taking into account the north-american notion of distance; which is drastically more roomy than in europe).
i've camped all over the redwoods in california. the best thing you can do is just drive around and see what you can find. they have reggae on the river every yearup on the eel riverso iliketo go the week after. tons of open camp sites and just enough cool people still around to meet new people and not feel crowded. i miss it a lot. it's been a few years since i've been able to afford to go, but if anyone is planning on going this year.. last august? early september? let me know. i'd love to meetup and hang out with some new folks.. maybe show you some of the cool hidden places.
i have found some good ones, big basin state park, its like an hour north of san jose and armstrong redwoods, thats a rec area, but they have camping. thats about 2 hours north of san jose. you can also check out http://www.parks.ca.gov/ if you click find a park, you can search by area, name, and activities.