Books
Leaders are learners, and one huge way to learn is to read books. There are hundreds of great books on leadership that have been written throughout the years. Here are several of these books that will help you grow in relevant leadership and ensure that your leadership is always in progress.
The Leadership Challenge by Jim Kouzes and Barry Posner
Built to Last by James C. Collins
Made to Stick by Chip and Dan Heath – http://www.madetostick.com/
Seven Habits of Highly Effective People by Stephen R. Covey