I was living in Massachusetts at the time and was driving home after some personal business in Pennsylvania. My route took me right through New York, but not into NYC. It was on all the radio channels, all the way home. For eight hours, I listened to every facet of news, analysis and discussion. I didn't have TV reception at the time, because I didn't have cable, so other than seeing the planes crash and the towers collapse, I didn't see the horrors of people jumping.
People were fleeing the city, driving north on the turnpike in NY just to get away. And the drivers on the road were very considerate of one another on that day. A lot of people made eye contact from their cars. People just wanted to reach out to each other, if only by sharing a look.
I didn't know anyone personally, but living in MA, I knew people who'd known some of those on the planes. I'd even heard of a few of them.
I think what stays with me the most is the horror of all those people trapped in the towers. It happened so fast, there weren't even very many people the rescuers could save.