I was on a stairstepper for this required gym class I had for college. The guy that supervises the gym ran over and flipped all the TVs to news stations. This was a few minutes after the first plane hit. I watched as the second plane smashed into the second tower.
Then I watched as one of the towers imploded. Peter Jennings didn't know what was going on, and I shouted, "The tower just imploded." Then (in what seemed like eternity, but was probably only a few minutes) he announced that the tower had imploded.
Our instructor allowed us out early, and I went back to my hall where every single TV was on, mostly CNN. I watched for a while and I believe I had class after but I don't recall the classes.
I remember walking into a building and people were surrounding the TV in the entrance.