There are so many #opened #oer repositories, especially helpful for #cc. I use Merlot https://merlot.org/merlot/.
I like OERCommons: https://www.oercommons.org/
And because I hail from Houston I am contractually obligated to mention OERTX.
https://oertx.highered.texas.gov/
Soon, my own cc will launch our own repository under the OERTX umbrella.