There are kind of converter too,which can remove DRM Protection from iTunes, Napster, Pandora, Spiral Frog and other online store,you can put removing drm video on digital media player: iPod,iPhone, Creative ZEN, Zune, PSP and other MP3/MP4 players.
I have used
Wondershare Music Converter to convert iTunes music to mp3, I t also remove drm wma, remove drm m4v, remove drm aac, ect.