Honeyman State Park ($3 day-use fee or Oregon Coast Passport [1]), three miles south of Florence [2], has a spectacular dune-scape and then some. Come here in May when the rhododendrons bloom along the short, sinuous road heading to the parking lot. A short walk west of the lot brings you to a 150-foot-high dune overlooking Cleawox Lake.
From the top of this dune, look westward across the expanse of sand, marsh, and remnants of forest at the blue Pacific some two miles away. This is also a popular place to camp (84505 U.S. 101 S., 541/997-3641 information, 800/452-5687 reservations).
Links:
[1] http://www.moon.com/destinations/oregon/background/sports-and-recreation/user-fees-and-passes
[2] http://www.moon.com/destinations/oregon/central-coast/florence