lucy24 - 1:27 am on Feb 17, 2012 (gmt 0)
In the US public domain is anything before 1923.
Material published by the U.S. Federal government has no copyright, ever. Does not apply to State governments!
Material published in the U.S. before 1989 without a copyright notice (in practice, this seems to apply most often to small university presses) is in the public domain.
Material published by Americans, in the U.S., before 1964 and not renewed is in the public domain. (Authors' descendants have been known to throw tantrums over this rule.)
Not all countries are Life+70. Many are Life+50. Some are Life+ more than 70. Some have special rules for special circumstances. Crown Copyrights run on their own schedule. Don't touch Peter Pan.