Best training apps

So I have just discovered the Nike training app...just completed my first 30 minute workout using it and wow I am dripping in sweat!! It has plenty of workouts for various time periods and for three levels of fitness. It has video footage of all the moves and you can play your music while doing the workout. All this plus it's FREE!!

Got me thinking if anyone else is using a training app that they love and gives them a good workout (even better if it's a free one!)