BCcampus open textbook: a selection of open textbooks for a variety of subjects and specialties.
Mason OER metafinder: searching resources across OER specific websites.
MERLOT: curated open educational resources, including textbooks.
OER Commons: open educational resources, including textbooks
Open Textbook Library: hundreds of open textbooks which can be searched for or browsed by subject.
OpenStax: high-quality, peer-reviewed, openly licensed college textbooks published by Rice University.
Open textbook initiative
Open texbooks for Social Work: many of these texts have relevance to related subjects such as sociology, psychology and public policy.
OASIS: openly Available Sources Integrated Search: a search tool that aims to make the discovery of open resources easier.
Teaching Commons: open educational resources from leading USA colleagues and universities.