The best wood is free wood. After that wonderful storm we had last winter, there are a whole bunch of knocked down trees and broken branches still being cleaned up. I'm sure you're like me and have driven past lots of potential sources. I stopped a few months ago and threw a 10' piece of maple in back of the jeep. It won't be fully seasoned until next year, but it's a start. I see lots of apple and pear trees around. If nothing else, the fruit farms probably have some blow downs you can have.
That said, I found an excellent Seattle area wood source! I picked up 20 pounds each of alder, apple and cherry wood from Joy & Ed, a family owned wood mill near the Southcenter Mall. Cost: $0.50 per pound. I found their advertisement on Craigslist.
This stuff is PRIME! Dried, cleaned and debarked fist sized chunks! Joy assured me that they have other wood types available. You will have to arrange for pick up. If you're local, it's well worth it. Give them a call at 206.243.6542