there are a few podcasts that I like - that I've gotten from ITunes -
Fitness Rocks is actually interesting - the doctor who runs it - will go thru a current medical publication and pull out the highlights of it... it's got some interesting stuff.
Fitcast has some interesting moments -the guy who runs it - is a 20 something canadian stoner who's primary job is a clerk at best buy - he's got some interesting interviews occassionally - there's a lot of stuff that just makes you roll your eyes but there are some good tidbits as well
The couch to 5K is a running program available as an ITunes download that is pretty well done too