What HR program has had the greatest impact on developing effective leaders in your organization?

I understand that we are given an option for a program'; however, my experience is that no one program or process meets the need for leadership development.  Mentoring and coaching are great tools, but they need to be supported with the right learning experience and practical development opportunities by working with peers and leaders on projects that bring value to the organization and employees.  

We use a multifaceted approach that includes formal development experiences, project assignments that provide growth experiences to ready the employee for the next step in their career development, and connection with mentors who support different development needs.