(1) LIBRARY OF CONGRESS AND THE BOOK BY THOMAS MANN ABOUT LIBRARY RESEARCH
Library of Congress Electronic Catalogue. You will be surprised to learn how much LOC can offer. See this book for details: Mann, Thomas. 2015. The Oxford Guide to Library Research. 4 edition. Oxford ; New York: Oxford University Press. Check out chapters on LOC's subject headings especially.
(2) OXFORD BIBLIOGRAPHY DISCIPLINE'S PAGE
There are several ways of searching for relevant sections in the Oxford Bibliography database. You can search within a particular discipline. You can search within the whole database, and I would highly recommend doing this because you can find some useful sections on your subject in a neighbouring discipline. But also it would make sense to look at the discipline's page where all the sections are put in groups of fields, and, what's more important, recently added sections are marked. Thus, if you monitor this page you can discover new sections which could be relevant. Additionally, check articles you need regularly because they are reviewed annually and new sources might be added.
(3) KNOWLEDGE BASES
(4) ARTICLES
(5) BOOKS
I would regularly read:
Explore book and paper prizes by thematic sections of professional associations, for example, www.asanet.org
(6) GRAY LITERATURE
Grey literature is a term used to refer to dissertations, theses, and working papers (also known as preprints). There are several repositories and search engines which allow one to find relevant sources:
(7) SYLLABI
Other universities invent more obscure names for this kind of thing. For instance, the University of Cambridge website does not have a centralised syllabi directory but many faculties publish their materials on their pages and name them "reading lists", "handouts", and "course readings". The one way to get these materials is to understand where they are usually placed on the University's website. In the case of Cambridge, you will find this under the "Current students" section of a faculty's page.
The Open Syllabus Project can show you the most-cited works from syllabi available on the public domain.
(8) LISTSERVS
You can also ask a question about literature on relevant listservs. Sociological listservs can be found here:
In English:
In German: www.hsozkult.de
Email lists by international and national sociological associations and their research committees and thematic groups are particularly useful:
(9) WEBSITES
There are websites which telegraph and create agenda in sociology. I would list the following websites:
I would also check the following book review and — wider — intellectual magazines:
(10) SOCIAL MEDIA
But there are also some other social spaces where information about literature is available in a more systematic way:
Software that facilitate finding citations:
(11) FOLLOWING SCHOLARS AND KEEPING AN EYE ON NEW PUBLICATIONS
Thank you so much. The info in the answer proved to be exceptionally handy and useful.