Disclaimer: I do not provide legal advice - this page, and all of our discussions today, focus on general information about how copyright works. For answers to specific legal questions, you will need to consult an attorney.BYU's own Copyright Licensing Office may be the right place to start!
Specific pages of interest:
Peter Hirtle's wonderful Public Domain chart!
American Library Association Office of Information Technology Policy interactive tools:
Public Domain slider, the Fair Use Evaluator, and the Exceptions for Instructors eTool.
Registering © (my own blog)
Copyright Librarian blog
@CopyrightLibn on Twitter