Mostly war, again. The beaches from the WWII Normandy invasion are facinating to see: the innovation of the Mulberry harbors, horror of the cemetaries, and scale of the assault are just a few examples. Bayeux is a lovely town, and the tapestry is a must-see.
We stayed at the Hotel de la Plage in Ouistreham (just north of Caen where the ferry to Portsmouth departs), and would highly recommend it. The food is a little heavy, but the cider and calvados are awesome.