I wish XM were the answer; it sounds good but in practice it's pretty unexciting.
Their "indie" stream, XMU, is programmed like a computer, playing the same odd handful of "indie" acts over and over and ignoring 98% of bands on the indie radar (including most bands on major indies, such as Drag City, Merge, Sub Pop, Rough Trade, Matador, Parasol, Yep Rock, Saddle Creek, Hush, Secretly Canadian, etc, as well as interesting bands on less prominent labels). They do play obscure acts but I never get the immpression they were selected for any special quality; it seems extrememly random (i.e. they sent us a promo so we threw it on).
They also steadfastly refuse to play any tracks older than 18 months (unless they're lazy and forget to take something out of the playlist; but they'll never play anything older than their broadcast debut).
One look at the playlist of WOXY or Radio@Netscape puts XMU to shame. For example, WOXY today played tracks from the new Low and 89 Cubs albums mixed in with classic Yo La Tengo and Built to Spill. A human might have actually programmed this. They're music fans and they're on top of things.
That said, XM is certainly better than terrestrial radio, but it's frustrating how bizarrely mediocre it is.
