http://tankmuseum.org/
I was there yesterday with Dad. Amazing place, it really is. They've got a complete history of armoured vehicles, from the original 'Little Willie' (don't laugh) prototype from 1915 to Challengers and Abrams' MBTs. Its not just tanks either- tank destroyers, self-propelled artillery, APCs, IFVs and even mine clearers and softer troop transports. Anyone else been or want to go?