As an instructor, there are a variety of ways you can use copyrighted material for teaching without having to ask permission - the trick is discovering what exceptions to copyright are most applicable to your situation. I recommend that you review the Framework for Copyright Analysis tab to help sort out your options when deciding how you can use the resources you want in your classes. However, these are the exceptions that are most applicable for instructors.
A note: The question I am most frequently asked is whether it is acceptable to link to online library resources in your course management system (such as Blackboard). Most of the library's databases permit this - for instructions on how to create persistent links, see Linking to Library Resources. For licensing reasons, it is better to link to the article rather than uploading the PDF directly to your course site. Additionally, linking directly to the resource you need for your class helps the ASU Library know how that resource is being used, which is one of the ways we make decisions about our collection.
Sharing a link to any publicly available resource is perfectly fine. As an instructor, you should avoid linking to anything that is obviously infringing - a movie that's currently showing in theaters on YouTube, for example - so that you can avoid giving the impression that copyright infringement is acceptable.
All Teaching Environments:
Public Domain (links to University of Minnesota Libraries) - A work is in the public domain if its copyright term has expired, or if it has never been covered by copyright (such as works authored by the U.S. Government). Works in the public domain may be used for any reason by anyone since copyright does not apply.
Creative Commons - There are a wealth of resources that are distributed under Creative Commons licenses, which already grant permission for a variety of uses. Most are applicable for educational purposes. CC Search has a collection of websites where you can find Creative Commons-licensed works.
Fair Use - the Fair Use exception needs to be determined for each particular use. Review the Fair Use Tab for more information. However, the ASU Library Reserve Policy provides some guidance for common scenarios for classroom use. While these are specifically for course reserve, they would be equally applicable to other course materials.
In Person Classes Only:
Classroom Use Exemption (included in Section 110(1) of Copyright Law) - this only applies to in-person, face to face instruction in a classroom at a non-profit educational institution, and allows for the performance or display of any copyrighted work without seeking permission. Playing a DVD or CD for a class (in whole or in part), singing a song together, or holding up purchased or borrowed copies of a book or artwork would be permitted under this exemption. It does not apply to making or distributing copies or to online instruction.
Online/Distance Education Only:
TEACH Act (included in Section 110(2)) - The "Technology, Education and Copyright Harmonization" Act allows instructors to perform or display copyrighted works in distance education environments. However, there are a number of restrictions - NOTE: The TEACH Act does not apply to MOOCs or the Global Freshman Academy - see Copyright and MOOCs for more information.
Here are some useful resources specifically related to the TEACH Act: