Ageism is prejudice or discrimination against someone based on their age. Ageism is most commonly aimed at senior adults, but can be directed at any age.
Old School: The Anti-Aging Clearinghouse has compiled an extensive list of free tools, books, blogs, campaigns, videos, podcasts, and more to help educate and fight against ageism.
The World Health Organization provides a ton of information and resources on ageism and ways to get involved.
The Silver Century Foundation promotes a positive view of aging with resources on various issues and so much more.