The #1 skill of an excellent leader is communication, or inter-personal skills. A good leader is a problem solver, and to do that he has know how to talk to people in a manner that is appropriate and which suggests respect for their level of expertise or knowledge in any given area. That is how a good leader gets results and inspires people to work harder and more efficiently.
#2 A good leader is not afraid to hire people who he deems smarter than himself. His goal is to build teams who will work together to get the job done.
#3 A good leader has a knack for knowing when to make changes and when to stay the course (in projects or management styles). He also understands the value of a compliment for a job well done. In addition, he rewards good work that consistently produces excellent results for the company--through bonuses, promotions, etc.