Welcome Tekgod!
I live in Seattle, and my fiance and I try to get out on day or camping trips whenever we get the time.
One of my old professors found a secluded campsite on Baker Lake, that sits on a small landing just before the lake; it's beautiful. You can probably fit 3-4 tents with a campfire in the area.
Because it's secluded and unmarked, he has specific directions to get there (he even has you reset your trip odometer at one point, and at something like 11.2 miles he has you pull to the side of the road!)
I'm out of touch with the guy now, but if I make contact with him, I can get those directions to you. Otherwise, there are plenty of areas to camp around Baker Lake, designated and undesignated, that are great during the summer time.
If you haven't been there before, take the Sedro-Wooley exit of off I-5. Head East on Highway 20 (or N Cascades Hwy), and eventually take a left on Baker Lake Rd. The lake will soon be on your right, and you're free to choose your camping area!
There is also a decent campground a few of my buddies go to on occassion, on Whidbey Island, called South Whidbey State Park.
Let me know if you have any regular spots that are worth checking out.
Take care