The Digital Comic Museum site hosts thousands of free Golden Age comics dating as far back as the 1930s. Although mainly US published, there are some UK and Australian titles available. All files have been researched by Digital Comic Museum staff and users to make sure they are copyright free and in the public domain.
To start downloading just register an account and enjoy these great comic books. There is no charge per download and the goal of the project is to archive these comic books online and make them widely available.