My household was a minor affair, we had little candles in the shape of the WTC on the dining room table. We would thank George Bush for the Patriot Act and then light the candles. We had to be good, because George Bush was always watching us with the Patriot Act, but if we were good, we'd get little pilot's wings pins.
The rich kids in my neighborhood had more elaborate plans. They had full on model WTC towers. If they were good, there would be RC planes under the towers on 9/11 morning. They were always showing me the cool videos when they destroyed the towers.
It's cool to hear how different cultures celebrate it. My family does WTC pinatas and 2 bats shaped like 747s. If you break them both in one swing, you get to cut the Iraq cake however you want (there's a little Saddam toy hiding in there that you get to keep it if it gets served your piece).