National Museum of the USAF
While on spring break at my parent's home in Ohio, my dad took us to the National Museum of the United States Air Force in Dayton. What an amazing place! The museum is arranged by era (early flight, WWI&II, Korea&Vietnam, cold war/modern) in four enormous hangers. There is also a small section with some space craft and missles as well as an outdoor exhibit of various aircraft.
While it is hard to pick a favorite, I really enjoyed seeing the large bombers and the stealth aircraft. Being able to walk through time from the early beginnings of flight to these giant beasts really makes you think about all the creativity, thought and hard work that has gone into making these advancements possible. It was also neat to listen to my dad who was on an aircraft carrier in Vietnam and my mom who's dad and brother both flew planes. Pretty special for both of them...
If you ever have a chance to visit while in the area it's free and worth more than the price of admission!