Wow. MSN Music does sound like a really good idea except for their focus, the payment thing, and the fact that it's Microsoft and probably Windows-only.
With the legal state of online music these days, I think you'd have a hard time doing that without charging for it, though. I wonder if you could possibly get enough money out of Amazon referrals?
What would be even cooler is to join up with some independent record stores. My local store is part of a coalition,
CIMS. I wonder if they'd have some interest in partnering up with something like this. Maybe you could have something where people could buy the albums from them, if they were local, for pickup. Anyway, I'm just talking out of my ass now.