On 9/11, Usher, Leonardo DiCaprio, and Tobey Maguire Give Back

By Jessica Gold Haralson

09/12/2008 at 12:10 PM EDT

Celebrities and politicians put aside their differences Thursday for a good cause.

Although they're rival presidential candidates, John McCain and Barack Obama came together for the ServiceNation forum, a non-partisan event at Columbia University. ServiceNation encourages Americans to get involved in public service. Both candidates agreed to back away from political attacks, instead discussing volunteerism, military service, and teaching.

The stars came out in full force: Usher, Leonardo DiCaprio, Glenn Close and Tobey Maguire all showed for the nationally-televised summit.

At the opening of the program, Usher was announced as a new youth advocate for Service Nation. At least one of the candidates is a big Usher fan: McCain recently told PEOPLE that he met the singer on the set of Saturday Night Live and that he "got to like him a lot."

According to his rep, DiCaprio was impressed by the call to national service.

Maguire gave a speech about the importance of service. Appearing right after New York Governor David Paterson, Maguire said the tragedy of 9/11 inspired him to give back.

"While I may play a superhero on the big screen, we all know who our real American heroes are," said the Spider-Man star. Some people in the 1,000-member audience were related to 9/11 victims.

Jon Bon Jovi will give the keynote speech today for the two-day summit.

• Reporting by LIZ MCNEIL