Campers and RVers will enjoy the amenities at Aqua Barn Ranch (15227 Renton-Maple Valley Hwy., 425/255-4618). The RV sites come with an indoor pool, a big-screen TV, and movies. Riverbend RV Park (17410 Maple Valley, 425/255-2613) has adults-only tent sites on 12 acres.
The wooded camping area on the east side of Dash Point State Park [1] (5700 SW Dash Point Rd., 253/233-03221) has primitive sites ($12), tent sites ($17) and RV sites ($23). The park is open year-round. Make reservations ($7 extra) at 888/226-7688 or www.parks.wa.gov [2].
During the summer between late April and early September, Saltwater State Park [3] (25205 8th Pl. S., Des Moines, 253/661-4956, www.parks.wa.gov [2]) also runs a small campground for tent campers ($17). There are no reservations, so get here early on the weekends.
Links:
[1] http://www.moon.com/destinations/washington/south-puget-sound/sea-tac-corridor/sights/dash-point-state-park
[2] http://www.parks.wa.gov
[3] http://www.moon.com/destinations/washington/south-puget-sound/sea-tac-corridor/sights/saltwater-state-park