From the U.S. Copyright Office, the Fair Use Index includes some (not all) decisions on Fair Use from multiple federal jurisdictions, including the U.S. Supreme Court, circuit courts of appeal, and district courts.
The sources collected here are frequently cited guides to copyright and Fair Use:
Common Scenarios is a good place to start. This page provides answers to common copyright questions that arise in the classroom.
Stanford Copyright & Fair Use is probably one of the most extensive copyright guides online. It's sponsored by Stanford University Libraries and Academic Information Resources, Justia, NOLO, LibraryLaw.com and Onecle
Copyright Crash Course was designed by the University of Texas, covers copyright and Fair Use, and was written by Georgia K. Harper, their Scholarly Communications Advisor.
LibraryLaw is a blog created by Mary Minow, J.D., A.M.L.S. The blog discusses copyright and Fair Use issues with special emphasis on libraries and their resources.
Copyright on Campus Video was created by the Copyright Clearance Center and presents the basics of copyright and Fair Use.
Fair Use Evaluator Tool was created by Michael Brewer of the Copyright Advisory Network. The tool helps users make Fair Use evaluations and can also collect and publish the information users provide in support of that use.
Fair Use Checklist is from the Copyright Clearance Center and provides a quick synopsis in checklist form of the factors used when determining fair use.
A Fair(y) Use Tale Video was created by Media Education Foundation. A funny commentary on Fair Use using Disney's own (fiercely protected) characters.
Know Your Copy Rights was created by the Association of Research Libraries and looks at copyright from an academic viewpoint.
Univ of Minn Copyright is the University of Minnesota's Copyright Information site. Includes a Fair Use Analysis Tool and a Copyright Decision Map.
Columbia Univ Copyright is Columbia University's Copyright Advisory Office. It has a Fair Use Checklist and model forms for asking for permissions.
Univ of Texas Copyright is the University of Texas's Copyright research guide. A good source for best practices in using materials for academic purposes.
Online Videos and Copyright links to the Code of Best Practices in Fair Use for Online Video created by the Center for Social Media. This is a great source for questions on using video in the classroom and in mash-ups.
Permalinks is the library's how-to guide on linking to database articles and ebooks in a way that doesn't violate the author's copyright.
CSU Quick Fair Use Tutorial was developed at CSU Maritime and provides specific scenarios about applying fair use in the classroom.