Mammals of the Pacific Northwest.
Forests of Washington State, with information on the trees and other plants
Wolf Population is a primer on wolf population management.
Edible Plants and Mushrooms of Washington State, useful for wilderness Garou.
Medicinal Herbs native to the area details the plants used for healing, as well as toxic plants.
Washington State Nature Resources Guide is a good first stop. The author has compiled websites detailing what birds, mammals, trees, and other wildlife are native to the state, with an extensive set of links.
The Burke Museum at the University of Washington has a wealth of information on the state's native species, including information on the habits and habitats of each. Their lists of mammals and native plants are especially useful. Best of all, pictures!
The Washington Native Plant Society. Pretty Pictures, Erudite Words.
Dr. Todd at the University of Oregon has compiled a number of scientific papers on the ecological effects of human activity on the Columbia River system, since the paleolithic era.
Small note: The GarouMUSH game setting is in a location that, in the real world, has very little in common with the game's environs. You may want to check with Wizards or more familiar players if you want to bring something into the game from the real-world location of the MUSH because of this.