Pandora is available for the latest Windows Phones. They have an offer for "ad free" through end of the year!
"Experience ad-free Pandora when you listen on your Windows Phone through 2013. Only Windows Phone has Pandora with no ads and no monthly streaming limit…for FREE. Windows Phone brings you the Pandora you love and gives it a unique Windows Phone twist, allowing you to pin your favorite stations to the Start screen, or see what’s playing by glancing at your Pandora Live Tile. "