I sync all my 'casts to an android phone rather than an mp3 player proper, but many of these are on my list as well:

Common Sense with Dan Carlin 
Dan Carlins Hardcore History Freakonomics Hacker Public Radio 
NPR - Planet Money
NPR - Fresh Air Radiolab 

If I could only have one podcast (gasp!) I think it would have to be Planet Money.  Astoundingly good.