The Library of Congress offers a variety of classroom materials as well as professional development to help teachers use their free materials effectively in their classroom. You can even organize and search material based on Common Core or State requirements. The Library of Congress contains a repository of primary resources in a variety of media (texts, images, audio, video, etc). Their professional development includes funded trips to the library to work at your own pace, free modules. Be sure to check out the Library of Congress’s Resources for Teachers.