I can make one negative suggestion: while I did enjoy listening to Rob Ingles' narration of
The Lord of the Rings, the parts about Frodo and Sam trudging through Mordor didn't exactly lift my spirits during August marathon training runs.
Basically I just listened to whatever my library had. I did enjoy several classes from The Great Courses, which are now available as downloadable content. The one on the Philosophy of Science was unexpectedly eye-opening for me. You should be able to track down a code for a free month with little effort.
Since then I've switched to podcasts, which are free and plentiful, and available on any topic you could possibly imagine. Between running and commuting I download about 20 hours per week, and each of those comes with back episodes amounting to many hundreds of hours. And it's zero effort: once I've found a podcast I like, new content just materializes. And if an episode isn't engaging, just skip it.