How about some ghost towns. We took a trip a few years ago and had a great time. We stayed at Condor Ore and checked out Fossil, Lonerock, Hardman, the latter is the ghostiest of the three, and I would not recommend taking any rig into Lonerock but if you have a toad and dont mind dirt roads that would turn your hair gray drive down to Lonerock. From there we went to La Grange and took an antique train ride and then drove to Joseph to see the artwork.
If you want some unusual scenery, John Day Fossil Beds are spectacular and you can't go to the town of John Day without stopping at the Chinese Doctors Museum.
Crater Lake was awesome and we stayed at the La Pine State Park. That area has some museums that should really be checked out. We snaked our way over to the southern coast and if you haven't been to the Redwoods, that is a must see, but just driving the Oregon coast is a great experience. Make sure you stop at Tillamook for ice cream.