From a human resources standpoint I think the best way for most of us to commemorate the attack on the US is to make sure our security and safety plans are in order. Do you have an evacuation plan? Have you done a fire drill? Do the employees hired in the period since the last meeting or drill understand what needs to be done? There is no better day of the year than this one to insure that in case of an emergency, be it natural or man made, all your employees can reach safety.
There were many compelling stories of 5 years ago of people reaching safety because they had a plan and had practiced the plan. I would hate for your story to be a sad one because you did not.