Hundreds of demonstrators gathered in Leimert Park Thursday night.
The 17-year-old was shot to death on Feb. 26 while walking to his house in Sanford, Fla. after a trip to the convenience store.
Police say a neighborhood watch leader, George Zimmerman, chased and shot the unarmed teen because he thought he looked suspicious.
Zimmerman, who claims he shot Martin in self-defense, has not been arrested.
The uproar over Martin's death has reverberated nationwide with demands for Zimmerman's arrest and scrutiny of police actions.
An estimated 8,000 people gathered at Fort Mellon Park in Sanford on Thursday night to hear the Rev. Al Sharpton give one of his trademark impassioned speeches.
Sharpton took the podium nearly an hour into the rally and stirred the crowd.
"Twenty-six days ago, this young man Trayvon Martin ... went to the store for his brother. He came back and lost his life," Sharpton told the cheering crowd. "Trayvon represents a reckless disregard for our lives."
Sharpton said he was angry at the handling of this case, and frustrated that Zimmerman had not been arrested.
"Enough is enough," Sharpton said. "Zimmerman should have been arrested that night. You cannot defend yourself against a pack of Skittles and iced tea."
Sharpton then introduced Trayvon's parents: his mother, Sybrina Fulton, and father, Tracy Martin.
"I stand before you today not knowing how I'm walking right now because my heart hurts for my son," Fulton said. "Trayvon is my son. Trayvon is your son. Thanks so much for your support."
Tracy Martin described his son as a "people's person" who did not deserve to die.
Just as the rally was getting under way, news came that Gov. Rick Scott and Attorney General Pam Bondi appointed a special prosecutor to investigate Trayvon's shooting death, removing the state attorney who had been considering the case.
Just hours earlier, Sanford police Chief Bill Lee Jr. announced he was stepping down from his post "temporarily."
"My role as the leader of this agency has become a distraction from the investigation," said Lee, brought down by a firestorm of criticism over the fatal shooting.
The Justice Department has also launched a civil rights investigation into the shooting.