The Society of American Archivists has released Orphan Works: A Statement of Best Practices.
Here's an excerpt:
"Orphan works" is a term used to describe the situation in which the owner of a copyrighted work cannot be identified and located by someone who wishes to make use of the work in a manner that requires permission of the copyright owner. Proposed orphan works legislation, such as the Orphan Works Act of 2008 (H.R. 5889) and the Shawn Bentley Orphan Works Act of 2008 (S.2913), would reduce penalties for infringement if an infringer "undertakes a diligent effort to locate the owner of the infringed copyright." This statement describes what professional archivists consider to be best practices regarding reasonable efforts to identify and locate rights holders. It is based on the authors' knowledge of the kinds of materials that are likely to qualify as orphan works