American Rhododendron Society:
http://www.rhododendron.org/
The American Rhododendron Society is a non-profit organization whose purpose is to encourage interest in and to disseminate information about the genus Rhododendron. Members' experience ranges from novice to expert. Society activities include public education, flower shows, seed exchanges, scientific studies, and communication through publications and local and national meetings. ARS chapters are located throughout the United States and Canada and in Denmark, Holland, Scotland, Sweden and Sikkim.
Rhododendron Society of Connecticut Facebook Page:
https://www.facebook.com/RhododendronSocietyOfConnecticut
Massachusetts chapter of the American Rhododendron Society:
http://rosebay.org