Repositories, Portals and Metasearch Engines for OER

There are special offers from the education sector that collect and make available Open Educational Resources (OER). These include repositories as well as portals and metasearch engines for OER. Here are some good search options for OER:

Openverse
Wikiversity
Twillo
Base
EconBiz
OASIS
MOM
OERhörnchen

In addition, there are many directories for open textbooks, which are worth searching.