Answer:
Every state has a parole board, although it may not be called that. The parole board reviews the cases of prisoners coming up for parole, and also hears/reads the petitions of citizens favoring or opposed to parole. By calling the parole board in your state, you can find out the procedures for filing such a petition, and where it should be sent. You may be able to appear before the parole board to make your feelings known in person.