My favorite podcast is Lexicon Valley. The show is pretty much described by its title. It has a chatty, friendly vibe that really proves the point - learning can be fun. And I have learned a lot about language listening to the all-too-infrequent shows that are posted on Slate's website (also avail on iTunes) - http://www.slate.com/articles/podcasts/lexicon_valley.html
Another Slate.com podcast that is enjoyable is The Gist with Mike Pesca. The show is somewhat humorous and covers current events (both weighty and light). I enjoy the easy flow of the podcast as well as its POV. I will confess to skipping over a couple of the regular segments. For instance, to me, having a song a week by They Might Be Giants, is a bit much. I used to love the band, but honestly, too much cleverness on a weekly basis starts to grate on my nerves after a couple of rotations. But the show is very solid otherwise. It can be found here: http://www.slate.com/search.html?wpisrc=burger_bar#search=the%20gist
Those who remember Dr. Drew Pinsky and Adam Carolla will like the Adam and Drew show on Carolla Digital. While the podcast is as self-indulgent as any other, it is just the sort of diversion that one can tune into (and out of) while on a long run. The two hosts are eminently accessible. Topics are drugs, sex, health, and a good dose of life-pro-tips. It is a fun show to add to your iPod. http://adamanddrdrewshow.com
Also on Carolla Digital is Penn's Sunday School. Magician, comedian, thinker, and atheist, Penn Jillete has created one of the most entertaining podcasts on the www. You don't have to be libertarian or atheist to enjoy this show. While a large portion of PSS is about all that goes on in the life of Penn, the show works because he leads a very interesting life, and has an interesting (if not always agreeable) take on the world around him. PSS is probably one of the top two podcasts I listen to on a regular basis. http://pennsundayschool.com
The main show that has been vibrating my eardrums lately during long runs is a spin-off of Penn's show called, Matt and Mattingly's Ice Cream Social. I really can't say enough good things about this podcast. After a couple of listens, you feel as if you are hanging out with old friends each time you tune in. I do have trouble listening to this on runs every now and then because I start laughing and it kills my pace. Here is a description taken from their website:
Twice a week, godless Las Vegas comedians Matt Donnelly and Paul Mattingly take on the news and issues of the day/week and end each episode debating a Jock vs. Nerd issue of the week/century. Matt Donnelly, co host on Penn Jillette's "Penn's Sunday School" podcast, and Paul Mattingly, co-host of the "Geek Shock" and "The Ugly Couch Show" podcasts combine to form a Voltron of hilarity. So in a drastic stretch of the imagination- this podcast is a Las Vegas Super Podcast. http://mattandmattingly.com
Finally, Henry and Heidi. My friend and editor of RUN, Mark Robison, recommended this podcast to me. While I liked Black Flag as a kid, I was never a fan of Henry Rollins. But Rollins and his co-host Heidi May, put out a podcast that is worthwhile. The stories are a behind-the-scens peek onto the lives of some of punk rock's and the counter culture's icons. Rollins has done and seen a lot. And Heidi is the perfect person to draw the stories out of him. The show is earnest, informative, and ultimately endearing (not an adjective I ever thought I'd use in reference to Rollins, but it is appropriate). I would highly recommend listening to this podcast starting at episode 1. https://itunes.apple.com/us/podcast/henry-heidi/id968474247?mt=2
So, if you are looking for some entertaining ear candy for runs, walks, jogs, hikes, or even simply mowing your lawn, the suggestions above should give you hundreds of hours of enjoyment.