On the same day it released iOS 6, Apple also dropped the latest version of OS X Mountain Lion. Version 10.8.2 adds new Facebook features including single sign-on, the ability to share links and photos via Facebook and the addition of Facebook notifications in Mountain Lion's notification center.
Apple also improved iMessage and FaceTime so that iMessages and FaceTime calls sent to your phone number will be also land on your Mac. There's also a handful of bug fixes that affect Twitter, AirPlay Mirroring, Safari and more. You can check out the full list on Apple's support website and download the update from the Mac App Store or by clicking on Software Update in the Apple menu.