ok- couldn't find the last few times we've done this... I'm sure I've forgotten a ton.
I've lived in NYC since the mid 80s- was living uptown, right on the hudson (96th and riverside drive) when this happened. I did consulting/free-lance and my own work back then, so my days were my own- no timetables or office to report to.
I was awakened at some point that morning by sirens- lots of sirens. I was up high and overlooking the river and west side hway, so not in the thick of typical NYC sounds. but sirens have always been omnipresent here, so you kind of tune them out... even a lot sirens like there were. I remember putting a pillow over my head to try muffle the sound, but then gave up... too many of them. I figured there was a bad car crash on the highway, and started my typical morning routine- go for a run. I opened a window, looked out over the Hudson towards NJ to a perfect, crisp and cloudless blue sky- honestly one of the nicest days (for weather) I can ever remember. in that moment, my only consideration was whether I'd wear a tank-top or a t-shirt for my run- the weather felt absolutely perfect and I was heavily considering each option... it was a very important decision.
as NYCers do before heading out, I turned on our 24hr local TV news station, NY1 to get the weather. that, of course, is when I realized what was going on.
like the rest of the world- I watched this all transpire on the tv. I remember calling my parents to let them know I was ok (I didn't have anything to do with the wtc, but felt I'd put their minds at rest regardless)... of course waking them up before it was even 6am their time (CA)- to "why are you calling?". they didn't know. I also called a couple of friends who worked in SF but commuted from marin and east bay- I wanted them to avoid the bridges, especially the golden gate.
I was on the phone with my bf's wife when the first tower fell- not realizing it, I collapsed too- absolutely bawling. I could hear the concern on her voice at my out of control crying- she hadn't turned on the tv yet.
I somehow got a hold of my gf (now wife) who lived in stuy-town (east and downtown, but not immediately near the towers). we talked briefly and planned to call each other back later- but without the towers, their was no cell service.
I decided to fill up my bathtub with water in case "they" went after the water system or reservoirs, and then went to the bank for cash and store for basics. the store- typical supermarket- was insane. it was like just before a hurricane with ALL the staples gone, people grabbing everything they could and throwing it shopping carts (at the time I remember feeling sad at how selfish everyone was acting). bank had a line of people taking out larger than normal bundles of cash.
it was at the bank- on broadway- that I noticed masses of people walking uptown... IIRC, even on the street. again, the weather was just perfect that day- and from where I was about 5 miles due north of the wtc, I couldn't see a single affect what had happened. all of the smoke was getting pushed south and east over brooklyn, so it stayed a perfectly blue, clear sky all day... the only sense that something was up was the migration of workers walking home (and even though nycers walk a lot, they don't commute that way) and the run on the bank and market.
just a crazy, horrible day.
an aside- a very gb used to live about 15-20 blocks north of the wtc on barrow st. we used to always joke about whether- if they fell- the towers would reach his place. when I was on the phone with my friend's wife, I had that thought in my mind as I watched the tower fall... thinking about how many city blocks full- entire neighborhoods- of apartments, stores, office, etc those towers were going to take out as they fell. I thought there were going to be 10s of thousands lost in those seconds. it was astonishing to see later how they pancaked down, leaving even some spots right across the street relatively damage-free.
eta: I will say- in spite of the selifishness at the supermarket- the next 6months to a year, I've never seen the city and it's people become as self-less from everything macro on down to tiny micro acts between people. it was amazing, even if we all knew it was never going to last.