These sites outline tools and techniques for identifying and contacting copyright owners.
"Orphan works" is a term used to describe works still under copyright for which the copyright owner cannot be identified, located, or contacted in order to ask for permission to use the work. The decision to use an orphan work without permission is a risk. The sites below can help you assess that risk.
With permission: Terry Owen and Andrew Horbal, University of Maryland Libraries and Cindy Kristhof, Kent State University Library