Was on my way to work when the first plane hit, heard it on the radio but it was mass confusion. Not a lot of confirmations at that time, just that there was disaster at WTC.
When I got to work and went through the break room; complete silence, all eyes on the TV. A little while later; the second plane hit.
I think people always remember where they were. When JFK was shot, when the Space Shuttle blew, when man walked on the moon … individually tailored for your personal favorite moments in sports, you knew where you were. Memories etched in stone forever.