NPR shows I'd probably grab as podcasts:
This American Life (I have complete set of them as MP3 files already)
On the Media
Marketplace
Car Talk
Wait Wait Don't Tell Me
I like roughly every third Fresh Air - There's way too many interviews with 60s-era rock stars, people who are largely wasting oxygen to begin with.
Talk of the Nation can be hit or miss, but hits WAY more often than not. My local station does "To the Point" instead of "Talk of the Nation", probably because it's cheaper to carry. I love the Science Friday shows best.
My local NPR station (wbez.org) used to run a show called Odyssey that I enjoyed a great deal. It was in the same general format as TotN and To the Point, but with a slightly more intellectual edge. I was really sad when the station management killed the show last year.