Postcast: In the Dark
Investigative journalism in podcast form was started off mostly by Serial, which most people have heard of (or have actually heard) by now.
In that same vein there is a new show out: In the Dark, by APM Reports. 9 Episodes about the disappearance of Jacob Wetterling, the case that shaped how the US deals with sexual crimes. Interesting, horrifying and shocking. Find it on iTunes, Overcast or Stitcher.