My family and I recently visted the Historical Electronics Museum (see http://www.hem-usa.org/ ) in Linthicum, Maryland. Along with an amazing treasure trove of defense electronics is a case containing several very interesting cryptology artifacts from the World War II era, including an Enigma machine. Pam thought it was the coolest thing in the museum, and we all spent quite some time admiring it, along with some other contemporary artifacts.
I you haven’t had the opportunity to vist the HEM, it is certainly worth the trip- it is very near BWI Airport right outside of Baltimore. It is free and open to the public, but be sure and check the hours carefully on the website, since they are a bit irregular. If you have kids, there are lots of great hands-on exhibits that explain electronics science and techology, which both my 11-year old and 8-year old daughters really enjoyed. Given that they wanted to go back again almost immediately, it is certainly a fun place for them.