If you want to switch apps, or go to the home screen without hitting the home button, you can use gestures. This lets you pinch in with five fingers from in any app to go to the home screen or swipe with four fingers from left or right to switch between open apps. You can also do a four finger swipe up for multitasking. Turn this on by going to Settings -> General -> Multitasking Gestures -> On.
Thanks to 101 iPad Tips & Tricks.