I love Mediafly! Make an account online, search through the subjects/topics....Add them to your favorites. They sync up with your phone. You can set it to auto download new episodes/programs. It's GREAT! love love looooove it!!!
Great support forum too

It's FREE!
I use Sleeptimerzzz with it; just set how many mins before it shuts down, select the "player" I want Sleeptimer to control (Mediafly), pop it in the multimedia dock and I'm listening to great content till I fall asleep, Sleeptimer shuts down Mediafly, and next thing I know my Droid is waking me up to the most obnoxious alarm sound I could find!