Nope. Steve Jobs specifically doesn’t like that idea for the iPod so it’s not likely to happen unless Microsoft’s new Urge software starts killing the iPod. There are a bunch of free podcasts which are kind of like having recorded a radio station onto your iPod, but nothing really like the subscription model.
I forgot to mention RealWorks Harmony. They had a subscription service that they hacked to wprk on the iPod even though they weren’t “supposed” to. I knew Apple had disabled it, but apparently it still works on the older mode iPods. See: