Scholarly and professional associations typically provide many of the following resources and services:
Locate associations by:
Sometimes a major national or international association may have regional subgroups or chapters.
There are associations devoted to a single person (example: Dante Society of America).
Metasites (general lists):
Literature and Languages:
Music: branches of the discipline and related associations:
Music metasites with more associations:
Art, Theatre & Dance
Many associations represent a whole discipline (history, literature) or branch of a discipline (American history, English literature), or other broad subject area (Renaissance studies, Romanticism). So you can start with a quite broad search, to see what the major association(s) are for your discipline, then add some keywords to see if there are any groups that specialize further in the subject area of your topic.
There are also associations devoted to a single person. So if your topic centers around a major writer, artist, etc., try searching their name combined with "association" or "society."