Outline Map of Washington
This is a basic black and white map showing the county lines as its only details.
Source: Indiana State University

Annual Average Precipitation Map
This map shows the average annual rainfall in the state.
Source: Spatial Climate Analysis Service, Oregon State University

County and City Information Map
Are you looking for information about a specific county in Washington? This map has links to general information about Washington counties, as well as a variety of sources dealing specifically with population, the economy, and county government finance.
Source: Office of Financial Management

Historical Population Density Maps
See the changing population of Washington from 1900 to 2000 in this set of maps.
Source: Office of Financial Management

Official Washington State Highway Map
This map is fully interactive with areas that can be enlarged.
Source: Washington State Department of Transportation

Washington State Map
If you need a map that shows the major freeways in Washington, this is a nice basic one.
Source: World Sites Atlas