The crowd met Tuesday near the wooded area where the toddler's remains were found in December 2008.
A nonprofit group that helps missing and abused children wants to build a memorial at the site.
Caylee's mother, Casey Anthony, was found not guilty in the child's death. She did not attend the memorial service, but Caylee's grandparents showed up.
They said they haven't had any contact with Casey Anthony since she was released from jail.