Thanks to a colleague of mine, Chris Fry, who posted these on the Podcasting Education group, I've come across the following podcasts that he thinks are suitable for intermediate students:
The 3 Monkeys Radio Podcast (their feed is here)
Crackle Back Short Stories (VoxPop Radio)(the feed)
Chris also likes the Bob and Rob show, and he says they "try hard to achieve a
balance between being slow and simple enough and being natural and
they are successful."
And here is the rest of it.