People killed in the attacks: 2,975 (official number as of Sept. 10, 2009)
Deaths of firefighters and paramedics responding to attacks in New York: 343
Nations with citizens killed in attacks (estimated): 115
Approximate percentage of Americans who knew a person hurt or injured in attacks: 20
Tons of debris removed from Ground Zero: 1,506,124
Economic loss of New York due to attack: $105 billion
FEMA money spent on the disaster: $970 million
People rescued alive from wreckage: 18
Days fires at Ground Zero kept burning after attacks: 99
Estimated number of New Yorkers with post-traumatic stress disorder due to attacks: 422,000
Estimated donations to 9/11 charities: $1.4 billion
Approximate units of blood donated New York Blood Center after attacks: 36,000
Amount the James Zadroga 9/11 Health and Compensation Act provides to first responders for health care: $1.5 billion will go to health benefits for the first responders, while $2.7 billion will go to compensation for them.
Estimated cost of New York 9/11 memorial: $700 million
The war on terror
American military deaths in Afghanistan: at least 1,645
American military deaths in Iraq: at least 4,474
Total combined cost of wars in Afghanistan and Iraq as estimated by Congressional Budget Office: $4.7 to $5.4 trillion
More stats at NYMag
Data: CBS News, New York Magazine, The National Post, The Associated Press (and here), Center for Defense Information