http://www.dancarlin.com/hardcore-history-series/
Engaging storytelling on some of the selected historic periods or events. Sometimes a little biased but well worth listening to.
In Our Time
http://www.bbc.co.uk/programmes/b006qykl
It can be hit or miss. But if you find a topic that matches with your interests it is usually very well covered.
The Ezra Klein Show
http://www.vox.com/ezra-klein-show-podcast
I like this guy and he usually has interesting guests.
Penn's Sunday School
http://pennsundayschool.com
Podcast of Penn Jillette (of Penn & Teller) usually pretty random but fun to listen to if you like magic, are an atheist or if you have libertarian views. Quality of episodes varies a lot.