USA.gov, the federal government's official web portal, recommends flying flags at half-staff, visiting 9/11 memorials and reading stories about 9/11 experiences as ways to commemorate the 9/11 terror attacks. Additionally, the Corporation for National and Community Service promotes service projects as a way to remember the 9/11 victims.
There is no federal holiday recognizing 9/11. However, the 9/11 non-profit MyGoodDeed was established to recognize the many Americans who choose to serve their country in the military, as first responders or through other official service opportunities. Other coordinated service opportunities can be found at MyGoodDeed's website. Local service opportunities for commemorating 9/11 are available in many areas through veterans' organizations and service groups. Anyone who cannot find local community service projects commemorating 9/11 can honor the deaths of victims and the sacrifices of first responders and the military by becoming active and starting such a community-based project.
Local museums and governments often create their own memorial displays for those who died on 9/11 and in subsequent military actions. Visiting these displays or coordinating one is another way to commemorate 9/11. The Library of Congress' September 11 Digital Archive is a repository of firsthand accounts and other materials related to the 9/11 terror attacks.