There are some amazing and powerful environmental movies that can be a great catalyst for discussion and change within the workplace. Organize a monthly or bi-monthly movie day for your employees to get them more engaged in your green initiatives. Show an environmental and thought provoking movie either at lunch time or a Friday afternoon.
Earth.org has a whole list of environmental movies that you can sort by category. After the film, engage employees in a discussion of how it applies to the organization and to their personal lives. Seeing the visual impact of environmental and social issues can be a compelling motivator for change.
Also go to eco-officiency business resources page for more environmental movie recommendations.