With the release of iOS 5, Apple gave us an even quicker way to switch between apps on our iPads. Before we start though, you need to make sure you have enabled Multitasking Gestures in Settings >; General.
Once this is enabled you have three gestures to help you navigate faster on your iPad.
1. Four or five finger swipe up - this will bring up your task bar just like double tapping the home key. Likewise using four or five fingers to swipe down restores you to what you were doing.
2. Four or five finger swipe left or right will switch between the most recently used apps. This is a gesture I use all the time especially if I'm referencing a web article, for say a blog (like this one!).
3. Four or five finger pinch will return you to the home screen from whatever app you are in.
If you haven't tried them, give them a go, they will make your iPad expeince a lot faster and better.