There have been lots of accounts of impressions from the day of the attack. My own feeling was that our enemies had made a serious miscalculation. Despite comparisons to Pearl Harbor, they had done no damage to our military potential, but this was sure going to piss us off.
The Coast Guard Compass has a whole series including a special issue of the Coast Guard Magazine and comments by both the Commandant and then Commandant James Loy.
I particularly liked this tribute to the mariners, both professional and amateur who aided in the evacuation of people from lower Manhattan.