Mason OER Metafinder
https://mason.deepwebaccess.com/mason__MasonLibrariesOpenEducationResources_5f4/desktop/en/search.html

OASIS
https://oasis.geneseo.edu/

OER Commons
https://www.oercommons.org/

Open Textbook Library (UMN)
https://open.umn.edu/opentextbooks/

Teaching Commons: Open Educational Resources from Leading Colleges and Universities
https://teachingcommons.us/

PDXOPEN: OPEN ACCESS TEXTBOOKS at Portland State University Library
https://pdxscholar.library.pdx.edu/pdxopen/

Cornell Open: A Global Open Access Portal
https://www.cornellopen.org/

Saylor Academy
https://www.saylor.org/

Community College Consortium for Open Educational Resources
https://oerconsortium.org/

OPEN (Open Professionals Education Network)
https://open4us.org/

Open Education Consortium
https://www.oeconsortium.org/

Utah Education Network OER for Middle School Courses
https://www.uen.org/oer/

Lumen Learning
https://lumenlearning.com/

Open Education (SPARC)
https://www.sparc.arl.org/issues/open-education

Open Educational Resources (Wikipedia)
https://en.wikipedia.org/wiki/Open_educational_resources

Open Educational Resources (Hewlett Foundation)
https://www.hewlett.org/programs/education/open-educational-resource

Open Course Library (Washington State)
https://opencourselibrary.org/

COOL4ED
https://www.cool4ed.org/

Open Book Publishers
https://www.openbookpublishers.com/