Now that I had picked out an architect, the first step was to find some land. Pb Elemental helped me out by pointing me at several available land listings around the Seattle area. There were a few good ones, but nothing that really caught my eye.
It turns out that the search ended rather quickly. About two weeks after I started looking for land, a new listing showed up in the Madrona neighborhood that looked very enticing. The land is located behind two duplexes. It's a large backyard that the owner had subdivided. Here's a satellite view of the lot below:
There's currently a large bush in the middle of the lot and no driveway, but the lot has plenty of potential. It's in a very quiet location, there seems to be ample parking everywhere, and I can see bits of Capitol Hill from the northwest corner of the lot.
Since I know that this is about as good as it's ever going to get in my price range, I put in an offer and reached mutual acceptance within a few days on 7/18/2010.