Northern California coast roadtrip recommendations?

Mendocino, maybe? See bpeoples' response in http://www.fluther.com/disc/138/what-is-a-good-weekend-getaway-near-san-francisco/

Still Water Cove is a great campsite my friends family goes to every year. Good trails both away from the water and down to the beach. You can rock pick in the cove for abolone.

No matter how you cut it, Hwy 1 is spectacular. The only question is, how much time are you willing to sacrifice on a winding road? If you go to Stillwater Cove on Hwy 1 (following the other recommendation), you should stop at nearby Fort Ross (historic Russian fort). And when you get as far south as Jenner, you can either head south to Bodega for some fresh seafood or head inland on Hwy 116 along the Russian River to Guerneville and go for a walk through the Armstrong Redwood forest. It's a beautiful deeply shaded forest, a great treat on a hot day where it is usually ten degrees cooler or more than outside. About twenty minutes further inland (along River Road, not 116 anymore) will take you into the wine region of Sonoma County. Drive around and get your friend drunk in little cottages and barns: the wineries are much less ostentatious than Napa and you're more likely to get free tastings. Closer to the GG Bridge, you might take another detour and go to the Point Reyes lighthouse, a fantastic lookout and the windiest spot in North America. Dodge cows and fly over the Marin Headlands to get there. Incredibly scenic. I just had a picnic there.

I forgot to add: the Point Reyes park has tons of hikes of various lengths. Most of them are windy:
http://www.nps.gov/pore/planyourvisit/hiking_guide.htm

The shaded Armstrong Redwood forest hikes tend to be short (< 2 miles), the longer hikes are hotter and hillier:
http://www.parks.ca.gov/?page_id=450

Stop at the Redwood National Park hq. They'll help you find a nice hike. I went mountain biking there once on a trip to Portland and ran into a zillion elk. It was amazing!
http://www.nps.gov/redw/

If you pass through the Mendocino Area the Jughandle Creek Farm is a great place to stay. Reasonable, hostel accomodations in a beautiful old farmhouse. Short walk to the beach and a good hike up to the pygmy forest--an awesome site. Check out their website:

http://www.jughandle.creek.org/

You should DEFINITELY spend some time around Del Norte County in the Smith River Recreation Area (which is adjacent to the Northern End of Redwood National Park). If you have time to do some backpacking there, "Devil's Punchbowl" will blow your mind. As you go South, you should definitely hit up "Fern Canyon" or the "Big Trees Loop" in the stretch in Northern Humboldt. Also, where the Klamath River meets the ocean often has whales if you go in the winter time. It's a pretty spectacular vista from a hill up there.
The Eel River is beautiful, but you'll it's a little South of Ferndale. If you continue to drive south on 101, you'll be driving along the South Fork of it and lots of great swimming holes abound there. You should definitely also take time to go to the Lost Coast and the King Range. Head into Shelter Cover and do some hikes there or even more spectacular is to drive through Ferndale and enter the King Range from the North. It's stunning.
I would also say if you have some extra time, go into Round Valley and Covelo and go swimming in the MIddle Fork Eel. It's a spectacular river with amazing swimming holes and is rarely visited. You're almost guaranteed to see bear in the Yolla Bolly Wilderness, which is right there.
Small towns worth stopping in: Arcata, Laytonville, Ukiah, Willts, and if you go along HWY 1, Mendocino.
But as others have said, you can't go wrong. It's a spectacular area!

Thanks for all the awesome recommendations! Here's what we did: On the way from Oregon to Ferndale we hiked in Patrick's Point State Park which was breathtaking. The next day we drove the entire Avenue of the Giants (old-growth redwoods) and stopped along the way to do more hiking, through some of the tallest trees in the world. They were absolutely jaw-dropping, and my lungs felt rinsed by that clean, clean air. Later on we found an organic burrito shack in the very cute town of Garberville for lunch, and another couple hours down the road we stopped and walked around the galleries and shops of Mendocino. Sadly we didn't have time to do any swimming in the Eel River, or any of the other great hiking suggestions, but we already want to go back to that area and play some more! In the meantime, I highly recommend both Patrick's Point and the Avenue of the Giants to any future travellers.