This site has a plethora of information on age, age inequality, ageism, Alzheimer's disease, and gerontology. Resources include professional organizations, journals, reference, discussion groups, and mailing lists.
From Oxford Reference: "A large national organization in the United States that advocates on behalf of Americans in the older age groups, roughly 55 years and older. There are equivalent organizations in most other nations in the Organization for Economic Cooperation and Development (OECD), i.e., upper-income nations. See http://www.aarp.org."
From their website: " the oldest and largest interdisciplinary organization devoted to research, education, and practice in the field of aging. GSA’s principal mission — and that of our 5,400 members — is to advance the study of aging and disseminate information among scientists, decision makers, and the general public."
The NCOA is the nation’s leading nonprofit service and advocacy organization representing older adults and the community organizations that serve them. Their goal is to improve the health and economic security of 10 million older adults by 2020.