I was in Austin at the time, and riding the shuttle to my British literature class. I noticed that the shuttle had very few people compared to normal.
I got to class, and about a third of the class was missing. Estimation, of course, cause it was a class of about 400-500.
The Professor was late, and when he walked in, talked about people being worried about family members, and dismissed the class. At this point, I still had no idea what happened.
I went back to my apartment, and saw on the news what happened. I forgot if any of my 3 roommates were there at the time or not.
I remember my sister being scared, because she had just started work in a tall building, on like the 10th floor, but not in NY. That's about all I can recall.