Someone just posted a link to their account of a drive north up the Oregon coast and part way up the Columbia.
I already mentioned taking WA20 across the state, as opposed to I90. Fo you want to go through the Seattle and Portland metro areas, or bypass them?
For camping I mostly use state parks (both Washington and Oregon) and forest service. There are camping options all along the Columbia River, through out the Washington (and Oregon) Cascades, around the Puget Sound, and along the coast.
For jeep trails, look up the Washington Byways book (Tony Huegel), and a corresponding on for Oregon.
