Many of our customers, like me, now use an mp3 player to play their backing tracks on stage. The old days are long gone where we had to use reel to reel or cassette tapes and indeed the nineties when we all used minidisc are gone too. MP3 is the new format for backing tracks.
However, although mp3 is by far the best backing track format available, there is one slight little problem you need to address if you are to use an iPod or other mp3 player live on stage for playing backing tracks. The problem with mp3 players is that, at the time of writing this, mp3 players like the iPod and the Creative jukebox were not dedicated professional hardware mp3 players, but rather little personal stereo type players which are meant to fit in your pocket.
Despute the fact that they were not designed to be pro mp3 players, you can still use an iPod on stage without any problems. It just takes a little bit of setting up through your PA system and a little bit of tweaking.
My article on connecting an mp3 player to your PA gives step by step instructions.