If you have time... the mouth of the Columbia River has had a military presence since the Civil War. There are three forts that guarded the mouth of the river, Fort Stevens, Fort Columbia, and Fort Canby. Stevens has the most interpretive military equipment, Columbia preserves the wooden buildings associated with military installations, and Canby was left to go more back to nature. But, Canby houses the Lewis and Clark Interpretive Center and two lighthouses (Cape Disappointment and North Head). Stevens has the wreck of the Peter Iredale out on the beach. Astoria is an arts-oriented river town, lots of galleries, brew pubs, restaurants, and the Liberty Theater (that claims Clark Gable as an early actor prior to his movie career).
As you move south down the coast, there are a few climbs and curves that will slow you down. Please watch for cyclists, September is a busy month for bicycle touring on the coast and they also go the north to south route. As you climb up and around Neahkahnie Mountain (and it's a clear day), be sure to pull off and take in the vista. If you are so inclined, you can climb the mountain and the views from the summit are impressive.
Of course, stop at the Tillamook Cheese Factory. Yes, it has become a tourist trap, but the ice cream... sehr gut! They have RV parking. The 3-cape scenic loop was closed due to a landslide that they don't seem a hurry to open, but a drive out to Cape Lookout State Park for a night or two is very nice. If you drive up and over the cape, you can stop and hike to the end of the cape. There are remnants of a B-17 that crashed out there in WWII. If you like air museums, the Tillamook Air Museum is housed in a WWII blimp hanger that sits at the Tillamook Naval Air Station. The collection isn't as impressive as it once was as part of it was moved to Madras, OR a year or two ago. However, it's still fun to stand in the doorway and see just how big the building is.
I see someone has mentioned Newport... don't forget the Hatfield Marine Sciences Center, the original Mo's Clam Chowder house, and, (IMHO, the highlight of Newport) the Rogue Brewery World Headquarters.
People mention the Oregon State Parks - my favorites; Ft. Stevens (Astoria area south to Seaside), Nehalem Bay (Garibaldi up to Seaside), Cape Lookout (Tillamook area), Devil's Lake (Lincoln City) Beverly Beach (Depot Bay to Newport). Honeyman is a nice park south of Florence, OR.
I better shut up, my post is getting too long... have fun.
