Pennsound is a site with free mp3s of poets and other writer types reading their work.
I didn’t see any Dylan Thomas but they do have several trax of Getrude Stein reading short excerpts of her work. (I’m downloading them even as I make this blog entry.)
More that caught my eye:
Pennsound link to Donald Hall reading his work.
Samuel R. Delany’s radio play, “The Star-Pit”