Lot's of Mustang clubs in the state. Check out
Pacific Cascade Mustang Club's links page for a good list. There is a club in Oak Harbor, which isn't too far from B'ham, and I could have sworn that there is a club up in that neck of the state.
Also check out
Mustangs Northwest for info on the biggest Mustang show that I've been to. It's four days long, and pretty much covers every aspect of owning a performance car.
Tom in Tacoma already pointed out the site for Pacific Raceways. There is also
Bremerton Raceway and for you guys closer to the Canadian border, you might consider going to
Mission Raceway Park in Mission, BC.
Hope this helps.