Copyright laws provide protection for set periods of time. Although there are some variations and individual situations can be quite complicated (especially with works that have multiple authors) the following are the lengths of protection for the various broad categories:
Literary, musical, dramatic and artistic works:
Protection for the lifetime of the author plus 70 years from the end of the year in which the author died. So as I am writing this in 2009, any book originally written and published by an author who died in 1938 (or earlier) is now out of copyright.
Film:
Lifetime of author, plus 70 years. For determining this there are four authors: the principal Director, the Screenplay author, the Dialogue author, and the Composer of any original music, and the 70 years starts for the end of he year of the last to die! Hence, copyright tin films can last a very long time. In practice the copyright is usually owned by the production company that made the film.
Broadcasts, sound recordings, cable transmissions, performances:
In most cases, the copyright lasts for 50 years after the year in which the material was first made available to the public.
Typographical arrangements:
Protection lasts for 25 years from the end of the year of publication
Designs:
Unregistered designs can be protected for 10 – 15 years
Registered designs have a longer protection period of 25 years