I can't help with commercial campgrounds. But for others (working off the top of my head):
Washington State Parks (check the state website):
http://www.parks.wa.gov/838/North-Central-Region- Lake Wenatchee
- Lincoln Rock on the Columbia
- Alta Lake near Peteros (some fire damage)
- Perrygin Lake near Winthrop
- Rockport (day use only) (very old growth)
- Rasar (on west side of WA20)
- several on Whidbey Island
(there may a couple of county operated parks along the Columbia River)
National Forest (western ones start closing in Sept; eastern ones remain open for deer hunting season)
- several along US2 west of Stevens Pass
- several east of Stevens Pass
- several along WA20 east of Washington Pass
National Park
- several in North Cascades NP, west side. Cheapest of the public campgrounds.
http://www.nps.gov/noca/planyourvisit/camping.htm
