Someone on another board I lurk at suggested this amazing podcast zombie show, so I'll pass it on to you guys. It's like a TV show but with only voice acting. It's free to listen to on their website (or you can buy it on Amazon and iTunes) and it just finished it's second season. Each episode is divided into 3-4 parts with one part released each week. Once an episode finishes another starts two weeks later with one part of that episode each week later. I highly recommend it, it's really interesting and a good horror adventure.

You can watch it free on their website, to get to the first episode you'll have to scroll down on the flash player to "Chapter 1 - It Begins - Part 1 of 3" and work your way up from there:
http://www.zombiepodcast.com/The_Zombie ... sodes.html

It's called a Radio Play. Very common.