I recently visited the Flight 93 National Memorial in Pennsylvania. The park is new and well laid-out and highly recommended. There are signs off the highway to direct you to the park and it seemed very well attended when I was there, on a beautiful Friday afternoon.
There are a series of introductory displays as you enter the park. This display shows the crew and passengers on Flight 93. You can see that there weren't many of them that day.
There were many parents with their children in hand. I could hear them trying to explain what the park was about, and it was difficult. September 11, 2001 was over ten years ago, and I have several nieces born since then, and other relatives too young to remember what 9/11 as it happened.
The wall is made up of 40 panels, one for each of the crew and passengers who died that day. Prior to the wall there is a black angled wall of sorts that is lower and you can see over it. I heard one of the park rangers explain that the lower black wall was to keep visitors off the open field which is a memorial site yet let them see where it occurred.
Flowers were left in front of several of the markers, and there were niches in the black wall prior to these panels where others laid out remembrances to soldiers, firefighters, and pilots.
Here is a brochure from the park. I am going to give it to my parents since they probably won't have a chance to visit Pennsylvania and see it in person. I highly recommend attending if you are in the area.
Cross posted at Chicago Boyz