For Oregon, head to the link and download the Front state map. It has a guide to vehicle access-
Trans Dev / Transportation Data GIS Unit Map Products
As for camping, I am not sure. I know places like Sand Lake (near Tillamook) have restricted their camping areas to the designated campground.
from some googling, probably best to verify the info below with Oregon Dept. of Parks and Recreation-
"Ok, I just called the Oregon Parks and Recreation Department (800-551-6949). I was right: camping is legal, except where prohibited.
The no-no's are:
-- No camping in areas that abut state parks;
-- Not within the city limits I mentioned above;
-- and not where signs are posted prohibiting camping.
Anywhere else, within the bounds of safety, common sense, and good taste, is fair game. The person I spoke to said that they have closed down a bunch of areas where large numbers of people used to camp, due to excrement and trash issues -- this may be code for "homeless encampments" or "hippy party spots," I don't know. But if they haven't posted a sign saying "no," and you aren't next to a state park, you are legal."