Jack Becker said
A lot of the state owned airports in WA and OR allow camping on the field. And some local, small Port owned do as well. KORS is owned by the local Port District. It allows camping, charges less then $10 per night and has showers, loaner car, etc.
We've plane/camped at Stehekin, Tonasket, Packwood and Manzanita. All were good, though the state park at Manzanita deserves special mention. It's a campers dream. Pacific Ocean 1/2 mile from the landing strip, standard park camping facilities, Nehalem Bay right off the end of the strip and town is about 1 1/2 mile walk. No loaner car though.
On our list still to do are: Seku, Westport, Ce Elum, Gran Coulee, Colville, Cavanaugh Bay, etc...