From VolunteerNYC.com:
GALLOP, a New York City-based nonprofit corporation offers therapeutic riding lessons to individuals with disabilites at the historic Kensington Stables in the East Windsor Terrace section of Brooklyn, near Prospect Park.
GALLOP is always in need of volunteers to help out with our program in ANY way! No horse experience is necessary, but it does help. We provide all the training you will need. We need people to help out at the stable with the horses and riders during lessons. Also, we have tons of "behind the scences", such as office work, fundraising, grant writing, etc. (more info)