Double swipe up [webOS 2.x & 3.x]
This tip is only for devices running webOS 2.0 and higher
If you want to open up the App Launcher when you are already in an app, the standard way to do that is to swipe up or press the home button to minimize the app to card mode, then either swipe up again or tap the launcher icon ( ) in the Quick Launch Bar to access the Launcher. While you can also drag up from the gesture area of webOS phones to access the Quick Wave Bar, there is no such single-gesture option for TouchPad users.
However, a "double swipe up" gesture that was snuck into webOS 2.0 and continued into webOS 3.0 allows you to go directly from an app to the App Launcher. Just swipe up with two fingers from the bottom of the screen and you will see your app minimize and the app launcher quickly appear.