This tip is handy if you ever fall asleep listening to music.
After you've selected a song in the Music app, head to the the clock app.
Select the timer option in the bottom right hand corner and set a specific time.
Below the time, there is an option that says, "When Timer Ends ..." tap that.
At the very bottom of the list is an option for "Stop Playing." Select this and when the timer is up it will stop the iPod from playing