Tool from the American Library Association that can help you find out if a work is covered by U.S. copyright, calculate its terms of protection and learn about Fair Use and other copyright exceptions
The Public Domain Slider is a tool from the American Library Association to help determine the copyright status of a work that is first published in the U.S. Requires Flash player.
Stanford's Copyright Renewal Database is a searchable index of the copyright renewal records for books published in the US between 1923 and 1963. Note that the database includes only renewal records, not original registrations, and only Class A (book) renewals received by the US Copyright Office between 1950 and 1992.