In an otherwise-moving piece, The Washington Post errs on the salute:
While opposition to the war has been stronger and more visible on the East and West coasts, small towns in the heartland and the South have provided the Bush administration with some of its most steadfast backers. But that support has cracked amid the echoes of graveside bagpipes and 21-gun salutes, which have been heard with greater frequency in recent months in small Midwestern communities.
From the Army: Today the national salute of 21 guns is fired in honor of a national flag, the sovereign or chief of state of a foreign nation, a member of a reigning royal family, and the President, ex-President and President-elect of the United States. It is also fired at noon of the day of the funeral of a President, ex-President, or President-elect.
In the United States, the 21-gun salute is used as a Presidential Salute as well as a Salute to the Nation when fired at noon on Memorial Day — a 50-gun salute (one gun for each state of the Union) is fired at noon on the 4th of July.
The 21-gun salute is not to be confused with the 3-volley salute using rifles for most military service members or shotguns for police officers at their funerals.
Gun salutes are also rendered to other military and civilian leaders of this and other nations. The number of guns is based on their protocol rank. These salutes are always in odd numbers.