I recently did a review of SongMaster Pro which is pretty good at this (and a lot else). It has a feature that lets you create stems for drums, bass, vocals, guitars, piano and the rest. You can create as many or few of those tracks as you want. Anything not separated out is put in the "rest" track. I have used it and I think it works very well although it's not perfect.  SongMaster Pro has a lot of other features for learning a song including the ability to speed up/slow down while pitch adjusting. It will also let you pitch adjust a song at full speed that is tuned down but you don't feel like re-tuning your guitar (for example some recently added Green Day songs!).