Since I already noded
Eastern Washington, I might as well do
Western Washington too.
Western Washington is where most of Washington's civilization resides. The major population centers are Seattle, Tacoma, Olympia (the capital), and, to the north, Everett and Bellingham.
Western Washington's geography is like none other I've ever seen. According to UW's geology department (and the Burke Museum of Natural History there) Washington was once an island attached to its own tectonic plate, drifting towards a sizable hole in the North American continent. When it collided, the result was a whole slew of varying terrain. There's the Cascade mountains, the San Juan archipelago, the Olympic Peninsula, the Olympic mountains, a rainforest, Mt. Rainier, and Puget Sound.
Western Washington is usually divided into the East Side and the West Side. The East consists of everything to the east of Lake Washington (the lake which Seattle overlooks). The west is everything else (including Seattle itself). The East Side is mostly soccer moms and yuppies. Microsoft is on this side, for those of you who wonder where to aim your ICBMs. The West Side has a little more variety. From Seattle to Aberdeen, for example, there is a world of difference, as you go from trendy metropolis to folk life and park rangers
The Olympic Peninsula is mostly reserved for retirees who like the weather and the ocean. Throughout most of that area it's very peaceful and quiet, one-horse-town kind've stuff. Port Angeles is a good example. All the peninsula which does not lie on the coast is national forest.
The San Juans and most of the archipelago in Puget Sound is for rich retirees and tourists. Some islands, such as Vashon Island are an exception to this rule. The peninsular-like landmass that makes up Kitsap County and Bremerton is rather dreary. This is probably because, for whatever reason, Seattlites do not want to build a bridge but, instead, insist on using the ferry. While this is a cute tourist trap it's a killer for commuting and so the area is rather deserted.
To the south of Tacoma and Olympia is a rather deserted stretch of land. This probably has something to do with Mt. St. Helens and Mt Rainier being there.
And that's about all there is to it.