Three of my favourite podcasts have to be Stuff You Should Know, Stuff To Blow Your Mind, and Stuff You Missed in History Class. They're light, but highly informative, and comedic. I think my favourite episode is from Stuff to Blow Your Mind called Stuff To Literally Blow Your Mind. LOVE these podcasts!
I'm also a fan of the Stuff 'casts. We save up our Stuff You Should Knows for road trips, but I listen to Stuff You Missed in History Class on early work mornings (you know, those days when I get here before the sun has even started poking up and even the janitors aren't here yet – peace and quiet). I was a little bummed when Deblina left, and then Sarah, too, but the Pop Stuff girls have taken over and I think they're holding up well.