WATCH LIVE: Ground Zero 9/11 memorial service in New York City
From the Archives: 11th Anniversary of September 11th terrorist attacks
WATCH LIVE: Vice President Biden speaks at the Flight 93 memorial in Shanksville, Pa.
Canadian PM pays tribute to 9/11 victims
WATCH LIVE: President Obama, First Lady attend Pentagon memorial
Mitt Romney's schedule for Sept. 11
Obama's schedule for Tuesday, Sept. 11