I pick and choose among my subscriptions--I usually just want a good story and to learn a little something--but I most enjoy:
Hardcore History - http://www.dancarlin.com/disp.php/hharchive
Intelligence Squared - http://intelligencesquared.com/podcast
To the Point - http://www.kcrw.com/news/programs/tp
Radiolab - http://www.radiolab.org/series/podcasts/
Bill Burr's MMP - http://www.billburr.com/podcast
Bookworm - http://www.kcrw.com/etc/programs/bw
On the Media - http://www.onthemedia.org/podcast/
The Mental Illness Happy Hour - http://mentalpod.com/
In Our Time - http://www.bbc.co.uk/programmes/b006qykl
