The activity I'm involved with which has probably done the most to develop my leadership skills is being a member of SDN, particularly in the role of Sr. Mod. 🙂
Laugh if you want. It involves leadership both by example and training others, with plenty of practice in self-restraint, demonstrating respect for others, treating others fairly, knowing when to pull the power card and when to let others take the lead. The biggest payoffs are watching others become confident enough to make their own good choices, and the interaction that goes on behind the scenes, where we get lots of experience working together as a team and drawing on each others strengths and experiences, in order to work for everyone's best advantage.
The most difficult part is having to do the right thing by playing the heavy when others persist in making poor choices.