There is a wide range of material that you may provide to your students in person in the physical classroom. You are encouraged to make use of materials not protected by copyright (see Alternatives to copyright), materials available under Creative Commons and open access licences, and your own unpublished materials, for which you do not require any permissions. Alternatively, you should make use of any applicable Exceptions to copyright.
Note: if you are unsure as to what you are permitted to do with a work, remember that emailing your students a link, which directs them to the material in question, is always permitted! For more information on creating persistent links, see Linking to full-text articles and e-books.