UPDATED! THIS VERSION IS COMPATIBLE WITH iOS 7+ ONLY.
SBMusic (formerly iSpringPlay) will let you add your iPod music playlists, as icons, to the iPhone/iPod and iPad springboard/home screen. Simply select the playlist from the list, set the icon caption and select the icon image. You can use the default icon image or select your own image. When you tap on the icon, the playlist will begin to play -- there is no need to launch the iPod app. From the creator of iBlank and SBPhoto.