Also don't miss Yad Vashem in Jerusalem - the holocaust memorial. I found the Washington, D.C. Holocaust Museum to be more informative from an academic perspective, but Yad Vashem is much more powerful, especially with its surroundings.

In the north, Rosh Hanikra, the grottos on the coast at the border with Lebanon, is pretty neat, especially if you go on a somewhat windy day, when the sea is "angry". Just don't leave ANYTHING in your car - we had our rental car broken into in the parking lot there. Once the thieves see you go down the cable car, they know you aren't coming back anytime soon.