So a friend reminded me about Phillipe Petit, the man who walked a tightwire between the Two Towers...which then reminded me of the picture book I added to my classroom library last year: The Man Who Walked Between the Towers.
For little ones who don't remember the events of 9/11, or are too young to experience more documentary-type books about that day, this is a way to connect them to that place in a less traumatic fashion.
For more mature children, those who are able to make emotional connections with people and events beyond their home communities, I recommend 14 Cows for America. This truly speaks to the worldwide impact of September 11th, 2001, as well as to the sympathy and generosity of a tribe halfway around the world. This book reminds me that 9/11 may have started off as an ugly act against humanity by humans, but it evoked so many more acts of kindness, compassion, and bravery--and who doesn't like to be reminded of the better, more beautiful side of our species?