Breakthrough: There is now a database you can check to see if a monograph's copyright was renewed. A big improvement over searching the catolog for copyright entries year by year. http://www.scils.rutgers.edu/~lesk/copyrenew.html
According to Michael Lesk, Carnegie Mellon University sent the records to India where they were scanned and proofread by Project Gutenberg Distributed Proofreading. Michael then ran the lookup with 150 lines of PHP. The more recent years were screenscraped from the LC site.
The database covers works from 1923-1963. Before 1923, U.S. works are in the public domain. After 1963, works got automatic renewals. The database covers monographs only, no scores, audiovisual works, etc.
This database is a big deal. It means that library digitization projects can FINALLY easily check renewals. U.S. published works from 1923-1963 that were not renewed are in the public domain. See Peter Hirtle's chart and look at published works for more detail.
Thanks to Christa Easton and Megan Prelinger for alerting me to this resource.