Look around your school, community, church, parks, etc., for projects that will help make it better for people and the environment.
Contact local nursing homes, shelters, food banks, schools, local governments, parks, zoos, crisis nurseries, daycare programs, domestic violence shelters, or other creative locations where girls can share their time with their community.
Keep in mind that some projects are limited by the age of the volunteer. If you are interested in volunteering at an agency, it would be a good idea to contact them ahead of time to be sure the girls are old enough to participate.