Jennifer Urban sez, "I'm happy to say that the Samuelson Clinic at Berkeley has just released a handbook to help folks research whether older items (pre-1978) are still under copyright in the U.S., or are in the public domain." This is probably the most esoteric question that normal people from all walks of life have to answer routinely; the Samuelson Clinic has really done an important public service here.
Interestingly the project originated with the Student Nonviolent Coordinating Committee Legacy Project, "a nonprofit organization run by civil rights movement veterans that is creating a digital archive of historical materials."
These educational tools help users to evaluate the copyright status of a work created in the United States between January 1, 1923 and December 31, 1977—those works that were created before today's 1976 Copyright Act. Many important works—from archival materials to family photos and movies—were created during this time, and it can be difficult to tell whether they are still under copyright.
The handbook walks readers though a series of questions—illustrated by accompanying charts—to help readers explore whether a copyrighted work from that time is in the public domain, and therefore free to be used without permission from a copyright owner. Knowing whether a work is in the public domain or protected by copyright is an important first step in any decision regarding whether or how to make use of a work.