[iOS] Game Center

Game Center for Developers
Game Kit Programming Guide

iOS SDK: Game Center Achievements and Leaderboards - Part1
iOS SDK: Game Center Achievements and Leaderboards - Part2

How To Make A Simple Multiplayer Game with Game Center Tutorial: Part 1/2
How To Make A Simple Multiplayer Game with Game Center Tutorial: Part 2/2

Game Center memory deallocation (with Cocos2D)
Game Center memory leak