Both beSpacific and Creative Commons provide pointers to the news reported on the blog Inside Google Book Search that Google Book Search now has copyright data for pre-1978 books, enabling users to determine whether books are in the public domain:
“How do you find out whether a book was renewed? You have to check the U.S. Copyright Office records. Records from 1978 onward are online (see http://www.copyright.gov/records) but not downloadable in bulk. The Copyright Office hasn’t digitized their earlier records, but Carnegie Mellon scanned them as part of their Universal Library Project, and the tireless folks at Project Gutenberg and the Distributed Proofreaders painstakingly corrected the OCR.
“Thanks to the efforts of Google software engineer Jarkko Hietaniemi, we’ve gathered the records from both sources, massaged them a bit for easier parsing, and combined them into a single XML file available for download here.”