Pedantry: the aircraft at the Museum of Flight is actually an M-21 blackbird (with a D-21 drone attached), not an SR-71 blackbird. It's the only surviving M-21.

There are about 20 SR-71s in museums (plus an SR-71 cockpit at the Museum of Flight, which you can sit in.)

Sources: http://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird#Accide... plus personal knowledge as a former Museum of Flight employee

Likewise the Airbus plant in Toulouse, France. You can see A380s being put together in one of the world's other largest buildings. The tour is usually in French but highly worthwhile even if you don't know the language.