I was sitting in my office when a lady in my office said that a plane hit the World Trade Center. At that time she didn't know much more than that and I assumed it was cloudy in NYC and a private plane hit one of the towers. I had a meeting downtown Pensacola at a US Courthouse that morning and caught all of the news on the way. I called my wife to let her know what was going on. When I went into the Courthouse all of the cell phones had to be surrendered, so we all sat that there for two hours not knowing what was going on. My wife called me over and over again frantically trying to reach me; not knowing that I didn't have my phone, but knowing that I was sitting in a Federal Building. The entire day was surreal. I will never forget it.
Edit: My brother was in a hotel near the Pentagon that day and wasn't able to get out of DC for 3-4 days.