Center for Creative Leadership
Center for Creative Leadership (CCL) is the leading nonprofit institution dedicated exclusively to leadership.

Leader to Leader Institute
Leader to Leader Institute was established in 1990 as the Peter F. Drucker Foundation for Nonprofit Management, and furthers it’s mission—to strengthen the leadership of the social sector—by providing social sector leaders with essential leadership wisdom, inspiration and resources to lead fro innovation and to build vibrant social sector organizations. 
  
Leadership Excellence
Initially formed in 1984 by Ken Shelton, Stephen R. Covey, Ken Blanchard, and Charles Garfield, the web site for Leadership Excellence features helpful tips on wiser ways to live and lead.
 
Robert Greenleaf author of “The Servant as Leader”
The Greenleaf Center for Servant-Leadership is an international, not-for-profit institution headquartered in Indianapolis, Indiana. Their goal is to help people understand the principles and practices of servant-leadership; to nurture colleagues and institutions by providing a focal point and opportunities to share thoughts and ideas on servant-leadership; to produce and publish new resources by others on servant-leadership; and to connect servant-leaders in a network of learning.

Smart Leadership
SmartLeadership has a mission to empower leaders to achieve personal influence through integrity, innovation, and intelligence.