Getting started with Cocoa
http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/CocoaFundamentals
http://www.amazon.com/dp/0321503619/?tag=stackoverfl08-20
Getting started with Objective-C
http://developer.apple.com/library/mac/#referencelibrary/GettingStarted/Learning_Objective-C_A_Primer
http://cocoadevcentral.com/d/learn_objectivec/
http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ObjectiveC
AppKit
http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/AppArchitecture
Blocks (closures)
http://developer.apple.com/library/mac/#documentation/cocoa/Conceptual/Blocks
Objective-C Garbage Collection
http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/GarbageCollection
Sample Code & Tutorials
Basic Cocoa & Graphics
/Developer/Examples/TextEdit
/Developer/Examples/CircleView
* /Developer/Examples/OpenGL/Cocoa/GLImageWall
http://developer.apple.com/library/mac/#samplecode/CoreAnimationKioskStyleMenu/Introduction/Intro.html
http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/CoreAnimation_guide/Articles/Headstart.html
Free Videos on iTunes
2007 Mac OS X Platform Overview
2008 Intro to Mac and iOS Development
2008 Getting Started with Objective-C: Coming from Other Languages
2008 Cocoa Fundamentals
2008 Multicore, Blocks, and Grand Central Dispatch
2007 Cocoa Drawing Techniques
2007 Bringing your Java App to the Mac
2008 Building Great Java Apps