(AP) - With familiar rituals of grief and a new purpose to honor those who rushed into danger to help, the nation marked eight years since the Sept. 11 terror attacks Friday, with volunteers reading the names of the World Trade Center lost.

Memorials in New York, at the Pentagon and at the crash site of United Airlines Flight 93 in Pennsylvania all took place under gray skies, and those reading names at ground zero spoke under tents to protect against rain.

President Barack Obama, observing his first Sept. 11 as president, had signed an order declaring it a day of service. He had first lady Michelle Obama marked a moment of silence outside the White House as a bugler played taps.

The president said the nation came together after the attacks, "united not only in our grief but in our resolve to stand up for the country we love."

In Shanksville, Pa., bells tolled for the 40 victims of the fourth hijacked jetliner that crashed there eight years ago.

At the trade center site, volunteers - from soup kitchens, advocacy groups, the Red Cross, the United Way - joined relatives of the lost to read the names of those killed in the twin towers.

Around the country, Americans packed up care packages for soldiers, planted gardens for low-income families and painted abandoned, boarded-up homes. The anniversary was declared a day of service for the first time this year to honor the spirit of those who rushed to the burning towers to save lives.

Umbrellas bloomed and whipped inside-out at ground zero, where moments of silence were observed at 8:46, 9:03, 9:59 and 10:29 a.m. - the precise times that jetliners struck the north and south towers of the trade center and that each tower fell.

Relatives and friends of victims visited a partially built, street-level Sept. 11 memorial plaza that had not been there a year ago. The memorial will ultimately include two square pools evoking the towers' footprints, with victims' names surrounding them and waterfalls cascading down the sides.

George W. Bush, whose presidency was defined in part by that day, had no public appearances planned. A spokesman said he would be working in his office. In a statement, he said he and his wife, Laura, were thinking of the victims and their families.

He also honored members of the armed forces and law enforcement.