Beyonce and Jay Z joined the Florida teenager's mother as she spoke to crowds in Manhattan alongside the Reverend Al Sharpton.
The case has become a flashpoint in separate but converging national debates over self-defense laws, guns, and race relations.
Scroll down for video
High profile: Trayvon's mother Sybrina Fulton, third from left, was joined by Beyonce, Jay Z and the Rev Al Sharpton
Connection: Celebrity couple Beyonce and Jay Z say as parents they can understand the pain of the verdict
The Rev Al Sharpton's National Action Network organized Justice for Trayvon rallies and vigils outside federal buildings from noon in at least 101 cities, from New York and Los Angeles to Wichita in Kansas and Birmingham, Alabama.
On Saturday morning he told supporters in Manhattan he wanted a rollback of stand-your-ground self-defense laws.
'We are trying to change laws so that this never, ever happens again,' he said.
'We have the strength to wipe our tears away. Last Saturday we cried. This Saturday we march.'
Trayvon's mother, Sybrina Fulton, also spoke at the New York rally, telling the crowd: 'Today it was my son. Tomorrow it might be yours.'
Emotional: Trayvon's mother Sybrina Fulton is joined by her son, Jahvaris, left, and the Rev Al Sharpton
Speech: Trayvon's father, Tracy Martin, tells crowds in Miami he will continue to fight for his son
Rally: Crowds gather outside the federal courthouse in Miami as part of a nationwide response to the verdict in the George Zimmerman case
She added: 'Of course we are hurting. Of course we are shocked and disappointed, but that just means we have to roll up our sleeves and continue to fight.'
Ms Fulton, her son Jahvaris, and the Rev Al Sharpton joined the rally as it marched to One Police Plaza at noon, where they were joined by Jay Z and his wife Beyonce, according to the New York Post.
Although they did not speak at the rally, the Rev Al Sharpton told the crowd: 'Jay Z told me, "I'm a father. Beyonce is a mother". We all feel the pain and apprehension - the laws must protect everybody, or it doesn't protect anybody.'
He added: 'We do not come from hate, we come from love of children,' according to the Huffington Post.
Beyonce had shown her support for the case last week, asking for a moment of silence at a concert after the not guilty verdict was recorded.
While Trayvon's mother was in New York, the dead teenager's father took part in a Miami rally on Saturday morning, according to NBC News.
Support: People march through Oakland, California, as part of the Justice for Trayvon rally
Verdict: George Zimmmerman, right, was found not guilty in the shooting death of Trayvon Martin, left
Debate: The rallies, including this one in Los Angeles, were organized to call for civil liberty charges to be brought against Mr Zimmerman
Wide spread: Philadelphia residents took part in the day of action
Campaign: In Austin, Texas, crowds marched while carrying banners
United: In Salt Lake City residents gathered outside the Wallace Bennett Federal Building for the rally
Tracy Martin told supporters outside Miami's federal courthouse: 'I vowed to Trayvon, when he was lying in his casket, that I would use every ounce of energy in my body to seek justice for him.'
He added: 'I will fight for Trayvon until the day I die. Not only will I fight for Trayvon, I will fight for your child as well.'
The Rev Sharpton and other supporters want the Justice Department to pursue federal civil rights charges against Mr Zimmerman.
He told the rally on Saturday: 'They will not say that was the young man killed in Sanford. They will say that was the young man who helped change the laws in the United States of America.'
Former Governor Eliot Spitzer, who attended the New York rally, said: 'Regardless of how you view the legality of the verdict in isolation, justice here was denied. An innocent young man was shot and killed and that is a tragedy.'
Protection: Eight-month-old Tyleigh Gould in Florida was one of many children taken to the rallies as parents voiced concern at the trial verdict
Presidential backing: At the New York rally a woman holds a sign of President Obama, who said he could have been like Trayvon Martin
Icon: Members of the crowd wore hoodies or held up packets of Skittles in reference to Trayvon being shot as he returned from buying the candy
National outcry: Rallies were due to be held in about 100 cities across the U.S. including Midland, Texas
Attorney General Eric Holder announced this week that the department would investigate whether the Hispanic neighborhood watch man could be charged under those federal civil rights laws, which would require evidence that he harbored racial animosity against Trayvon.
Most legal experts said it would be a difficult charge to bring.
Mr Holder added that the shooting demonstrated the need to re-examine stand-your-ground laws nationwide.
The Rev Jeffrey Johnson told about 200 people in Indianapolis that the rally was about making life safer for young black men.
The Rev Johnson said there were still endangered by racial profiling, and he compared Mr Zimmerman’s acquittal to that of four white officers in the beating of black motorist Rodney King in 1992, according to the Boston Globe.
'‘The verdict freed George Zimmerman, but it condemned America more,' the pastor who is a member of the board of directors of the National Action Network, said.
On Friday President Obama said it was still common for black men to ‘'be followed in a department store' while shopping or to walk down the street and 'hear the car doors lock'.
He added that he had experienced both scenarios before he rose to social and political prominence.
Network: The rally in Miami was one of many held on Saturday, to mark a week since the not guilty trial verdict
Change: The trial has led to calls for renewed debates on Florida's stand your ground law
Mass action: Large crowds gather in Atlanta, Georgia, at one of the Justice for Trayvon rallies
Protest: A young girl joins a protest outside a Philadelphia court house