Two rallies were held Sunday in honor of the teen, and another is scheduled for Monday at Texas Southern University.
From local rappers to congressmen, black and white, the shooting death of 17-year-old Martin has set off a firestorm of emotions.
Investigators said Martin was killed Febrary 26 while walking home from a convenience store.
Self-appointed neighborhood watch captain George Zimmerman, 28, confronted Martin that night. He called 911, reportedly because Martin appeared suspicious.
Though Zimmerman was told not to follow the teen, he did. He claimed he shot Martin in self-defense.
Zimmerman was found armed and standing over Martin. He had a bloody nose and a wound on the back of his head. He has not been arrested or charged with any crime.
Martin had no weapon on him -- only a pack of Skittles and a bottle of iced tea. He was shot in the chest.
The hoodie he wore and the Skittles he was carrying are now a symbol of the ongoing battle, some say, for equality.
The Houston rallies Sunday were held in support of Martin's family and in pursuit of justice, participants and organizers said.
"Even after my death, I will continue this fight," Congressman Al Green said. "I will haunt the Congress of of the United States until there is justice for Trayvon."
Local demonstrators said what happened in Florida could have happened here.
"When there is injustice, we need to stand together," said Elliott Gershenson with Interfaith Ministries of Greater Houston.
At the first event, several hundred people gathered on the steps of Houston City Hall at 3pm. In unison, they chanted "no justice, no peace." Elected officials, the NAACP and church and community leaders led the rally.
Sunday's second event was held at 6:30pm at Emancipation Park. Community activist Quannell X led the prayer vigil and community rally, which featured appearances by Houston rappers Bun-B and Slim Thugg.
Both events hosted people from a variety of ethnic backgrounds. Many participants wore hoodies, as 17-year-old Martin did, and signed petitions in support of a wider federal investigation into this incident.
"No matter what your gender is, race is, it's heartbreaking. It really, really is," local resident Debora Evans said. "He should have been able to make it home."
"Life, liberty and the pursuit of happiness applies to all Americans," supporter Linda Johnson said.
An alleged witness has now come forward in this case, claiming he saw fight between the pair with Zimmerman on the bottom.
"That's pretty significant, but we dont know what happened before that confrontation," KTRK legal analyst Joel Androphy said.
Androphy said Florida and Texas law are virtually identical. What matters in this case, he said, is whether Zimmerman provoked a fight with Martin and whether Zimmerman ever backed off after that.
Androphy said a grand jury needs to judge that, not law enforcement. He said the case should be brought to a grand jury.
The justice department has launched an investigation independent of the local police. Congresswoman Sheila Jackson Lee said the case will be reviewed this week by the House Judiciary Committee meeting. She is a member of that committee.
The community rally on TSU's campus is scheduled for 3pm Monday. It starts in front of the student center.
A second rally will be held Monday at 5pm, at the Shape Communty Center on Almeda Road, in southwest Houston. People who attend are encouraged to wear a hooded sweatshirt like the one Martin was wearing when he was shot.
Lamar University NAACP is hosting another rally on Wednesday at 3:15pm in the Quad. A petition will be available to sign, and they are asking everyone to wear hoodies of any color or black T-shirts.