Professonal Societies for educators often provide a rich variety of services to their dues paying members, as well as offering resources to the public at large. Most education oriented professional groups publish a mixture of hands-on practical oriented magazines, as well as research oriented academic journals. Professional societies also are frequent compilers of statistics, as well as maintaining depositories for lesson plans. Professional societies also tend to offer professional development programs, which may include national or regional conferences, and offering assistance to locate grants or fellowships. In addition to offering nationwide services, many Professional Societes also offer regional, state or local chapters.
Advocacy Organizations are similar in nature, but typically draw from & offer services to a mixture of memberships coming from Teachers, School administrators, Local school boards, State agencies, Parents and Foundations. Advocacy organizations typically are focusing significant energy on shaping public policy, and less on personal development.
If you are looking for either a Professional Society or an Advocacy Organization that is not listed here, then you ought to search this resource: Education Resource Organizations Directory. This directory is maintained by the U.S. Department of Education, and provides access to over 2,800 education related organizations.
You can also turn to the Encyclopedia of Associations, which is a directory for all types of special interest groups, such as Trade Associations, Professional Societies, Hobby Enthusiasts or Lobbying Groups.