Swipe between full-screen apps with a multitouch trackpad in Mac

The key is three fingers.  From within System Preferences, take a look at the Trackpad settings and ensure that all of the gestures designated as More Gestures are enabled.  Once enabled, you will be able to navigate around your desktops and apps more easily.  Use three fingers to swipe left and right to navigate between your desktops and apps that are in full-screen mode.  A three-finger swipe up will reveal Mission Control and a three-finger swipe down will show Expose, which reveals all open windows for the currently selected application.  Add a thumb with a pinch to your three finger gestures to reveal Launchpad and the Desktop.  Another gesture that is new in Mountain Lion is the ability to use a two-finger left swipe from the right edge of the trackpad to reveal the new Notification Center