Getting started with Objective-C

• http://developer.apple.com/library/mac/#referencelibrary/GettingStarted/Learning_Objective-C_A_Primer
• http://cocoadevcentral.com/d/learn_objectivec/

Getting started with Cocoa

• http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/CocoaFundamentals

About Objective-C

• http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ObjectiveC

About AppKit

• http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/AppArchitecture

About Blocks (closures)

• http://developer.apple.com/library/mac/#documentation/cocoa/Conceptual/Blocks

About Objective-C Garbage Collection

• http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/GarbageCollection