Anyone who knows me knows that I'm a huge fan of radio and books-on-tape (or CD), and many of the full-cast audio books (performed by a cast of actors, rather than just one individual reading) have a wonderful old-time radio (OTR) feel.
There also is a great set of OTR CDs, issued a few years ago by Radio Spirits, called "The 60 Greatest Old-Time Radio Shows From Science Fiction Selected By Ray Bradbury" (how's that for a mouthful of a title?). Among those programs are dozens of famous SF short stories. I found myself listening to that while walking, driving, and just laying in bed imagining I was enjoying a circa 1940s/1950s radio broadcast.
Also, don't forget the Twilight Zone Radio Shows which we covered in issue 603 of Amazing Stories. Those are out on CD, too, and really do a nice job mimicking, while at the same time building upon, that OTR feel.