In Canada, copyright protection for most works, such as books, paintings and dramatic works, lasts about 50-70 years after the death of the creator, whether or not the creator still holds the copyright. If the creator died in 1971 or earlier, the period is 50 years from the end of the year of their death. If the creator died in 1972 or later, the period is 70 years from the end of the year of their death. After copyright expires, a work becomes part of the “public domain” and can be freely copied, distributed, adapted and performed without having to request permission from the author or having to pay any royalties.
For non-dramatic cinematographic works, it is generally 75 years following the date of publication. Due to historical changes to the Copyright Act, photographs taken prior to 1949 are also usually in the public domain.
Other works may be in the public domain because a copyright holder has chosen to not claim copyrights. The Reproduction of Federal Law Order, for example, permits anyone, without charge or request for permission, to reproduce Canadian laws and decisions of federally-constituted courts and administrative tribunals in Canada.
Some public domain works can be found at the Gutenberg Canada and Project Gutenberg websites. Wikipedia: Public Domain Resources also lists many public domain resources.