Movie stars occasionally did radio shows, and Dick Powell was a star in two eras in two genres (the song and dance musicals and hard boiled films noir a decade later). Powell's radio claim to fame was the long running series, Richard Diamond: Private Detective.
Richard Diamond was a good series, and Powell did a fantastic job in the lead role - his easygoing but tough style was perfect for the sarcastic dialogue that was written for the character.
This is a great place to start if you've never heard Radio Drama before. It's also a must-listen show if you're already a fan of Radio Drama. Great stuff.