Sometimes professors assign works that are in the public domain, meaning that they are no longer under copyright. For example, if you are in a British literature course, the works you read might be from the 18th or 19th centuries and their copyright may now be expired. If you think your assigned course materials might be in the public domain, it's always a good idea to check.
Here are a few websites with free access to public domain works:
Some professors are assigning Open Educational Resources (OER) for their courses here at Gettysburg. OER are openly licensed teaching, learning, and research materials which can be accessed and used for free as well as adapted and shared with others. For more information about OER, contact OER@gettysburg.edu or explore OER Commons.