Facebook
Single sign on for Facebook
Adds Facebook as an option when sharing links and photos
See Facebook friends' contact information and profile pictures in Contacts
Facebook notifications now appear in Notification Center
Game Center
Share scores to Facebook, Twitter, Mail, or Messages
Facebook friends are included in Game Center friend recommendations
Added Facebook "Like" button for games
Challenge friends to beat your score or achievement
Other new features
Adds Power Nap support for MacBook Air (Late 2010)
iMessages sent to your phone number now appear in Messages on your Mac*
You can now add passes to Passbook (on your iPhone or iPod touch) from Safari and Mail on your Mac*
FaceTime can now receive calls sent to your phone number*
New shared Reminders lists
New sort options allow you to sort notes by title, the date you edited them, and when you created them
Dictation now supports additional languages: Mandarin, Cantonese, Spanish, Korean, Canadian English, Canadian French, and Italian
Dictionary app now includes a French definition dictionary
Sina Weibo profile photos can now be added to Contacts
