I took my son to school and was listening to a local sports commentator who complained as he said something like, "We aren't a news organization, but I have been handed a memo to tell you that a plane has struck the World Trade Center." They preceded to talk about other crap after that so I thought nothing of it. I was reading a thread about the Bills that was really long before I left to take my son to school, so when I returned I stayed in that thread a bit and read some others before I went to the news.
From the way I had heard it on the radio, I had assumed it was a small plane. So it was a bit before I realized what had happened. I turned on the TV. The 1st tower had already collapsed, and they showed replay after replay of that. I was essentially just staring at the screen in shock. Then the second tower collapsed and to be honest it was another minute before it soaked in, that wasn't a replay of the first tower.
My mind immediately jumped to Osama bin Laden. Make of that what you will. I immediately woke my wife at the time and explained what was going on. I also had a couple of shots and became real concerned as it seemed like war might have been started (not saying it wasn't but was certainly not all-out).