OER and related materials can be found on multiple websites from multiple sources. These tools can help you find them:
The Google search engine has an ‘advanced search’ that lets you search by ‘usage rights’ for content published to the Internet under an open license. The Advanced Search dialogue can be found under the Settings function or can be directly accessed at https://www.google.com/advanced_search
Image source: https://www.cccoer.org/learn/find-oer/
For Health Sciences OER, see box below.