Around Seattle you have Walker Valley to the north and Reiter Pit to the east which was closed for a long time but was slated to reopen sometime soon I think. There's Tahuya over on the peninsula and Evan's Creek to the south.
Walker Valley and Tahuya require the Discover Pass thanks to the grand wisdom of our corrupt and inefficient government.
Most of Tahuya can be done with a stock Jeep. So can Evan's Creek if I remember correctly.
. It's got a pretty good breakdown of what's around you and what they're like.