The Society of Psychologists in Management (SPIM)
The SPIM is directed at psychologists who are managers or transitioning into a management role. This organization hosts workshops and a yearly conference. http://spim.org/
American Psychological Association (APA)
The APA has a number of divisions that are relevant to management and/or leadership.
Division 14: Society for Industrial and Organizational Psychology (SIOP)
This website is focused on issues related to I/O psychology and provides information on conferences, resources, and publications. http://siop.org/
Division 18: Psychologists in Public Service Sections (Division Section: ...