Aviation
The Museum of Flight (Boeing)
The largest museum on the west coast, and definitely worth the trip to Seattle. You can book a group tour, and enjoy personalized attention. Or, you can visit the first Thursday of every month from 5-9 at no charge (courtesy of Wells Fargo). If you can afford it, the personalized group tour will be a lot less crowded and chaotic. But if you’re budget-conscious, the free night is also great. $5pp extra to use the flight simulator.
Evergreen Aviation Museum
Yes, this is all the way past Portland, but you can’t see the Spruce Goose anywhere else. They have Scout-specific aviation merit badge nights for $12pp. Or, better, attend the Merit Badge University in September. Camp out on their grounds on Friday, and be prepared for a full schedule on Saturday.