Sarvey Wildlife Center, even though it is waaaaay out in the sticks in Arlington, would be my first choice to take any injured wildlife–they are really wonderful. http://www.sarveywildlife.org/, and check out their “what to do if” page for general info on how to best help an injured or orphaned animal.
There are a couple vet clinics in the greater Seattle area who have “ambulance” pickups to go to Sarvey (but you need to make a donation to cover fuel costs) if you don’t want to take it there yourself. But yes, call first, and get their advice. In many cases an injured animal is best left on its own.
