Unpublished works created before 1978 that were published after 1977 but before 2003: Life of the author + 70 years or 31 December 2047, whichever is greater
Unpublished works created before 1978 that were published after 31 December 2002: Life of the author + 70 years
Unpublished works when the death date of the author is not known: 120 years from date of creation
"Work for hire" works would use the 120 years if they have never been published.
A "work for hire" published after 1977 get either 95 years from date of first publication or 120 years from date of creation, whichever is shorter (but still pretty darn long).
EDIT: This is a good website for copyright terms:
http://www.copyright.cornell.edu/training/Hirtle_Public_Domain.htm