Normandy has a number of sites worth a visit, Pegasus Bridge is a must do. St Lo, Carentan, Pointe du Hoc, Falaise, Merville, This tour might give a good overview if your time is short.
http://www.ddayhistorian.com/
You should also check out some of the Bulge battlefields like StVith, Spa, Malmedy and Elsenborn. There is also a December 1944 Museum in La Glieze that has a King Tiger on display amongst other interesting exhibits.
http://www.december44.com/anglais/index.html