The following resources are great. There is much to discover!
Website
Organizations and Agencies
Books
NOTE: Information and books are great but there is really no substitute for solid professional consultation by a qualified and licensed psychologist who also practices sports psychology. Dr. John F. Murray is qualified to handle both performance enhancment and clinical issues. This allows you as coach to have "one stop shopping" for your team to handle both serious issues that are disruptive to team unity and indiviudal well being, and to inspire and teach through proper mental training!