Check out docs.folio.org
The community is formalizing documentation at docs.folio.org. Make sure to check that out if you are looking for the most up-to-date documentation for specific apps.
Documentation for Specific FOLIO Apps
Apps keeping their most up-to-date documentation on docs.folio.org:
Documentation for Specific FOLIO Apps
Informal documentation to support tips on how to use apps and features in development.
Tips for Community Members
Dive Deeper
Guides to FOLIO Data