Battle of the Bulge Museum in Luxembourg. Wow, simply wow.
Fort Knox has been mentioned and they've a terrific display of tanks. There's a private tank museum in Woodside, California. They've a Pzkw I (yep, that little machine gun armed thing that the Germans thought was just a training tank and they put it into combat anyway), a PzKw IVf2 (so I think it is), several Shermans, T-34/76 & T-34/85, a Pzkw V Panther auf. A (they're restoring right now), Sdkfz-7 Prime Mover, Flak 88 (yep, the dreaded 88), Hetzer, Sturmgeschutz III, M-5 Stuart, JS-III (the 45 ton monster that couldn't be stopped by anything in our arsenal), British Conqueror (which was built to stop the JS-III), M7 Priest, etc.