Open Educational Resources are teaching and learning materials that provide users with (1) free and unfettered access and (2) 5R legal permissions to retain, reuse, revise, remix, and redistribute them, that can be used to replace traditional expensive learning resources (such as textbooks). You can use these web sites to find freely accessible content on the web which grants some or all of the rights listed above. See individual materials for specific permissions and rights. These materials include course modules, videos, worksheets, powerpoint presentations, and even entire textbooks, which can be linked to or loaded on your course page in Canvas.
The JET's OER coursemap suggests OERs and open textbooks that may work for specific classes. Scroll down to a course you are prepping for to see a few options you might want to consider. You can also contact a library liaison to help you gather other source material that may help you in creating course packs for your students.
Before you begin using OERs, you should evaluate the materials. Here are some things to consider:
The Canvas Commons has over 100,000 items you can easily import directly into your course page, including modules, images, documents, quizzes, even complete courses. To search, you must log into your canvas account, then choose the Commons icon on the left: