My experience is similar to others here... hearing from co-workers, trying to go online but the internet was running like mud because so many others were doing the same, hearing the second plane had hit, Jocelyn calling me crying, going home after seeing the first tower fall because it was obvious nothing of value was going to be accomplished on that day.
Back in the late 80s, I had stood on the observation platform at the top of one of the WTC towers. These buildings were so huge that it defied imagination that they could ever come down. When you stood next to one of them, it filled your whole world. And whenever we visited NYC they were the first things you saw as you drove through a pass in the New Jersey hills on I-78, and the last things you saw in your rear view mirror on your way home; their red beacons surveying all like red-eyed sentries at the southern end of Manhattan. I'd always thought they were ugly, but after they were gone, oh, the pang the first time we were back and they were absent from the New York skyline!
That was eleven days after the attacks. Guiliani had told people to come to NYC, and we felt we needed to be there, if only to convince ourselves it wasn't some gigantic Hollywood hoax, or maybe as an act of defiance to the terrorists that we refused to live in fear. So we went. The tunnels were still closed, so we actually had to cross the Verrazano Narrows Bridge into Brooklyn, then crossed the Brooklyn Bridge into lower Manhattan, but so many roads were blocked off it was hard to get around. Eventually we parked north of Canal Street and walked down. We saw the pile of destruction, still smoldering. An acrid smell hung in the air. We saw the iconic skeletal sections still standing upright, although we were kept at least a block away on all sides. I brushed some of the gritty concrete dust off a nearby building; it was everywhere, and shopkeepers were hosing down their awnings and storefronts. The cemetery at the church nearby was still filled with dust and debris. Everyone was quiet, respectful, somber. We saw all of the "have you seen this person?" posters plastered everywhere. We lighted two candles (red and blue) and left them among thousands of others, plus flowers, plush toys, posters, etc. in a nearby park. It all had a dreamlike quality.
The following month, I went to Arlington, VA to see the Pentagon. We stood on a hill where the Air Force Memorial now stands and saw the collapsed section in the E-ring. My father has since passed away, and he is interred in Arlington National Cemetery; if you go out the front entrance of his columbarium, you are facing the section of the Pentagon that collapsed.
The following spring I visited the field in Shanksville, PA. I saw the makeshift chain-link fence covered with keepsakes left by other visitors. A local told me that the impact site was under 24 hour guard, so not to try to approach any closer than the observation area or I could be shot -- not that I was inclined to try.
In some ways, the events of 9/11/01 seem like they happened yesterday, and in other ways it seems like it was a thousand years ago. It seems like every 10-20 years there's an event that makes everyone stop in their tracks -- the Challenger disaster, the Kennedy Assassination, Pearl Harbor -- and every time there's some kind of lesson learned, usually that we've been lax and complacent. It seems Americans have short memories and even shorter attention spans. But those of us who experienced 9/11, even if we weren't physically in NY, DC, VA or PA that day, will never forget it.