French City Pass - See More - Pay Less - Everyone Likes a Bargain

Paris, being the first, offers for many years past, a Museum pass that allows you entrance to over 70 Paris ( in and out of the city) museums. There is also a Paris Visite card that gives you unlimited transport on the Metro and Paris buses.

Now other major cities within France are getting on the bandwagon to do the same. 
Besides Paris - Lyon - Nice - Nantes  -Dijon offer passes that include discounts in the cities sites and transportation. All can be bought at the local tourist offices. 

If you are visiting Normandy and its War Museums - they offer a pass for only 1 Euro ( bought at the first War Museum ) you visit and  then is good for discounts at any of the scores of other War Museums spread out along the Normandy Coast.