You have been notified

The new Notification Center opens with a two-finger swipe from the right edge of your trackpad, and you can customize how things show up there in the System Preferences. Also note the options to Click to Tweet and Click to Post (to Facebook) at the top of the Notification Center for quick social network interactions.

Editors' note: The Facebook features are not available in this initial release of Mountain Lion, but Apple says they are coming in an update this fall.