Nope, they're not just for iPod owners and I believe most are free.
I absolutely love Photoshop TV and was stoked to see that they're releasing new episodes just for NAPP members. I occasionally check out the podcast at Tips From The Top Floor. I'd love to know more photography podcasts though.
Michael, would you be thinking about the Photoshop Killer Tips podcast? They're usually only a minute or two long.