The Waldorf school that serves the Eastside is Three Cedars -- www.threecedars.org
. As far as preschool goes, they have a parent/child program and two mixed-aged kindergartens (one for 3.5-4.5 year olds; one for 4.5-6 year olds.)
I'm not sure about other preschool programs. There are lots of Montessori schools. And, there are many, many preschools that focus on early academics, which is probably common in most areas.
I think there's a free magazine/brochure that lists schools/preschools on the Eastside. I'll see if I can find one while I'm out today. If it has a web link, I'll send it to you. If not, I can mail it to you if you'd like.
I'm no help with schools in Seattle proper, though my friends that go to the Phinney Ridge Co-op love it.