If you are a K-12 educator or parent, here is a very useful search engine for K-12 OER materials.
Easily is the key because frequently resources that seem to be open are not Creative Commons licensed and cannot remixed or shared. Thus, a teacher can use the resource but not modify it to meet their individual student needs or share it.
Easily also means you can find them easily. OCW is using a Google Custom Search Engine that anyone can place on their website enabling OER searches.
It is really easy to add this search engine to your blog or webpage.
The beauty of Creative Commons licensing is that it promotes sharing and enables individualizing instruction. If I want to remix the resource for my class, I am free to do so. There are six CC licenses all easy to use and free. Check the website for an explanation of all six licenses. Creators still retain copyright when they use CC licenses. They can license it differently on another website, if they choose.
Here are a few selected open websites licensed with Creative Commons licenses allowing for sharing and remixing, essential for individualizing instruction in the classroom.