USAF Museum, Dayton, OH. The vast bulk of the collection is indoors, though there is a good-sized display outdoors.
Main hangars:
http://maps.google.com/maps?f=q&hl=en&geocode=&ie=UTF8&t=h&ll=39.780764,-84.109558&spn=0.004221,0.009398&z=17
Memorial garden:
http://maps.google.com/maps?f=q&hl=en&geocode=&ie=UTF8&t=h&ll=39.779346,-84.112514&spn=0.002111,0.004699&z=18
Outdoor display (SICBM launcher in upper right):
http://maps.google.com/maps?f=q&hl=en&geocode=&ie=UTF8&t=h&ll=39.784771,-84.107557&spn=0.002111,0.004699&z=18
Annex: You take a bus here:
http://maps.google.com/maps?f=q&hl=en&geocode=&ie=UTF8&t=h&ll=39.785604,-84.096501&spn=0.002111,0.004699&z=18