When you are using your iPod function and are in the iPod interface, hold the the home button to quit everything.
Once you've done that, the title of the song you are playing would be on the screen saver, right below the time, on the locked screen.
Even when you are charging, like this.

Once you've done that, the title of the song you are playing would be on the screen saver, right below the time, on the locked screen.
Even when you are charging, like this.

