There has been liberal talk radio, but it tends to fail miserably. See en_ki's post about Air America. I think he's also spot on about why they fail. They seemed like such pretentious snobs. It's unbearable.

I think he's also right about NPR. I think a lot of liberals listen to that. I even listen, and I'm a conservative. I'd call NPR more moderate.

If you want a real laugh, look up Michael Savage. The guy is actually pretty brilliant, but his commentaries are psychotic. He's the most rabid of them all. It's part of his shtick.