Been to Sky quite a bit...I rather like them. Gotten more than a few pieces of material from them. Their outdoor bonsai table in spring and summer is pretty good! They also have an indoor bonsai corner with mostly Serissa, Zelkova, and various Ilex. What I really like is their regular nursery material; they have some good stuff! Nice little Mugos, a ton of different Juniper and cedar and spruce species, as well as any azalea, gardenia, and deciduous you could ask for.
Only been to Swanson's once when I was in the area and remembered I needed soil, and they sell Happy Frog, so stopped in. I didn't really get a chance to look around, but I will next time.
If you're ever up in the Marysville area, Sunnyside nursery is also an excellent nursery for folks looking for bonsai material.