The following books are some I highly recommend for those who are in leadership positions, or aspire to grow as leaders.   

While my primary interest is church leadership, I am fascinated by effective leaders in any sphere.  The books listed are not necessarily distinctively Christian.  I believe most, if not all, of these books would be beneficial for leaders in any realm. 

Wooden on Leadership  by John Wooden & Steve Jamison

Transforming Leadership by Leighton Ford

Spiritual Leadership by J. Oswald Sanders (of OMF)

The 7 Habits of Highly Effective People by Stephen Covey

Principle-Centered Leadership by Stephen Covey

First Things First by Stephen Covey

Good to Great by Jim Collins 

(Note Collins has also written a short, but excellent supplement to this book, titled Good to Great in the Social Sectors)

 Leading Change by John Kotter

 Excellence in Leadership by John White

 21 Irrefutable Laws of Leadership by John Maxwell

 17 Indisputable Laws of Teamwork by John Maxwell

 Agape Leadership by Alexander Strauch & Robert Peterson

 Top Ten Mistakes Leaders Make by Hans Finzel

 Ordering Your Private World by Gordon MacDonald

 Leading With a Limp by Dan Allender