This post from a year ago warrants a repeat.
As I watch, read and listen to tributes today, I wonder what I can do in tribute that would be enough. And, I think just remembering what happened and the people it happened to—some of them very very brave—and those who served following the tragedies, is what we all can do. Remember them in whatever way you do. But, do remember them. We need to never forget because some day someone will say it never happened.