Become an Xcoder...

Here's a little PDF download (2MB), outlining the basics of Xcode practices and Objective-C. The CocoaLab source of this download also contains good tutorials and some select Code examples.

You might not like the Objective-C syntax at first, but you will love its elegance in the long run (I guarantee it!).

Offline resources...

Two great books!

1. Cocoa Programming for Mac OS X by Aaron Hillegass

If you're serious about programming, and serious about Mac OS X!

2. Step Into Xcode by Fritz Anderson
Another great book, supplementing Aarons quite well!

Online resources...

Learning Cocoa and Objective-C

I've supplied these free resources for learning Cocoa, and for making the journey more pleasant with a few great tools.

Please add more, as you see fit, as long as they're of equal quality.

Object Oriented Programming @ Stanford University

Learn the Xcode basics, the Objective-C language, how to use Xcode and project-builder. Stanford University delivers slides, tutorials and problems for you to solve

Communication level:University,Programming experience:none

Apple Developer's Site

The official Objective-C and Cocoa frameworks API. You will also find downloads for all of the latest Xcode-versions and API documentation. Do create an account here... it's well worth it!

Cocoadevcentral

A place to learn Cocoa, providing tutorials and links to great resources to get you started!

CocoaCast - Podcast

A podcast which goes through several lessons, each describing a key-concept in Cocoa as presented in the book by Aaron Hillegass.

Great tools

Apple Developer's Site, members get Xcode tools etc.

This is a repeat, as it is a Must have!

AppKiDo

Ever wondered how to get to grips with all of those Cocoa-frameworks? AppKiDo shows the way!