Mentioned above, but these are our local shops with some details about what I think they excel at:
Maruyama (amazing azaleas, a few imported white pine, lots of black pine, hornbeam and juniper, several incredible collected Sierra juniper and a few ancient olives from an orchard currently in stock; best place to get pumice, lava and akadama - bring 5 gallon buckets)
Evergreen Gardenworks (mostly mail order, but can visit in person by appointment, terrific starter and pre-bonsai material)
Ron Anderson (newer nursery with some interesting stuff, plus closest to you and great people; good classes)
Lotus Bonsai Nursery (can visit in person by appointment, good pot selection, collected Sierra junipers and other mountain trees; classes and collecting trips available)