Want to know what radio drama has evolved to? Check out the Leviathan Chronicles, or many of the other drama podcasts that are finding their way to the web.
The Leviathan Chronicles is one that Ron found, and we have both been enjoying the story. It is high adventure, across continents and oceans. It can be found here. It was written by Christof Laputka, who works at a sound studio (I think) in New York. I get the impression that Christof is looking for a way to get his work "out there" in a techno-savvy format. I think he may have found a niche.
As a work of fiction, there are a few problems with TLC. Occasionally my willing suspension of disbelief has been stretched. Still, as entertainment, TLC works very well. The voice talent he found to bring the characters to life is good. The adventure is fast paced. There is suspense and mystery and entertainment. You can download for an MP3 player, or burn to a disc for a CD player. Either way is suitable for a road trip.