Hardcore History is a free podcast on various history topics. If you spend time commuting and need something to listen to, subscribe on you podcast player or check out this website:

http://www.dancarlin.com/hardcore-history-series/

Podcasts 50 through 55, "Blueprint to Armageddon" are on the Great War. I'm up to 54, really great stuff.

Unlike most podcasts, these are long, like 3 or 4 hours, so one can last you a few days in your commute, and Carlin is not a historian, he's a fan of history, so he reads bunches of stuff and talks about the interesting parts. Very worthwhile.