Perhaps the recent theatrical release of "The Hobbit" will make the following statement sound less dated, but I doubt it. Either way, I'm going to say it: UberTalk is the one audio streaming app (or site) to rule them all. By audio streaming, I mean live radio shows and podcasts. And by all, I mean a great many.
UberTalk lets you listen to 20,000 AM/FM radio shows and podcasts, according to the developer, Michael Robertson of MP3.com fame. Although the selection is large, UberTalk limits radio to terrestrial stations; sorry Stern fans.