OpenEd (formerly known as OpenEd.io) offers a huge index of educational games, videos, practice assessments, tutorials, and more. One of the strengths of OpenEd is that you can search for resources according to Common Core Standards and Next Generation Science Standards. Another of OpenEd's strengths is its integration with multiple learning management systems including Google Classroom, Otus, and Schoology.
Within the Otus learning management system you can use OpenEd to search for materials to share with students through your online bookshelf of resources.
From the OpenEd catalog you can share resources to your Google Classroom classrooms. Watch the short video embedded below to learn how to do that.
Schoology also has options for sharing OpenEd resources. I don't personally use Schoology so I haven't tried it. But judging by OpenEd's demonstration video it takes a little more time to set up than it does in Google Classroom or Otus. The video is embedded below.