This is an user's guide to archives outside of New York University Libraries. This is the definition of archives from the Society of American Archivists (SAA):
"1. Materials created or received by a person, family, or organization, public or private, in the conduct of their affairs and preserved because of the enduring value contained in the information they contain or as evidence of the functions and responsibilities of their creator, especially those materials maintained using the principles of provenance, original order, and collective control; permanent records. – 2. The division within an organization responsible for maintaining the organization's records of enduring value. – 3. An organization that collects the records of individuals, families, or other organizations; a collecting archives. – 4. The professional discipline of administering such collections and organizations. – 5. The building (or portion thereof) housing archival collections. – 6. A published collection of scholarly papers, especially as a periodical." Richard Pearce-Moses. "Archives." A Glossary of Archival and Records Terminology. Society of American Archivists, 2005.
These are published directories which are usually listings of archives, either as a list of what is owned by a specific institution or a list of archives in a topic. Sometimes it can be combination of the two. You should always remember that another source of archives is already published scholarship, where any archival collections should be listed in the bibliography. Dissertations often list archival collections as a specific section, so these can be extremely useful, especially for hard to locate collections (and institutions)
In searching Bobcat you can always use the keyword subject search "Archives Directories." If you add another term, a location for example, you can quickly limit the search. The trick is that not every possible term is used, and the third term may take out materials you would want to see, so fiddle with any additional subjects. For example, the search "archives directories Jewish" brings up three records, but does not bring up A Great Collection: The Archives of the Jewish Labor Movement because it does not have these three words in its subject headings.