Classic Movies in Radio Theater
Popular movies were often adapted into radio shows in the early to mid-20th century.
These shows are now in the public domain and are made available to download at the Internet Archive, which is like a museum of all things internet.
Some shows were so popular (or so old that everyone had forgotten about them) that the producers would rehash the stories with fresh actors. I love comparing the actors in the remakes to the ones in the originals.
The producers would often try to get as many of the original actors to play his/her part on the air, like Meet Me In St. Louis with Judy Garland (orig. broadcast December 2, 1946) or Gaslight with Ingrid Bergman (orig. broadcast April 29, 1946).