I do a fair amount of radio and podcast listening thanks to my day job. I have to say one of the best programs out there is Radio Lab. In fact, Radio Lab is one of the best programs I have ever heard in any media. Seriously, if you haven't heard it do your self a favor and check it out. It is a "science" show produced by WNYC, NYC's local public radio station. I say its a science show but its definitely made for non-scientists.
Here is a link to the show web page. There have been a few seasons of radio shows (a season is about 6 episodes) and all can be downloaded from the website or perhaps easier as a podcast on iTunes.
The editing of the show, the content, and the use of sound is amazing. Excellent, excellent stuff. Seriously, go listen to it!