Categorically Speaking
- Article from Stepwise on the merits of Objective-C categories, with examples.
- http://www.stepwise.com/Articles/Technical/CategoricallySpeaking.html

Objective-C Beginner's Guide
- Tutorial in text and code samples. English, Chinese.
- http://www.otierney.net/objective-c.html

Cocoa: The Objective-C Programming Language
- A detailed introduction to object-oriented programming in the context of the Objective-C programming language.
- http://developer.apple.com/documentation/Cocoa/Conceptual/ObjectiveC/

Objective-C is Fun
- A simple introduction to Objective-C, from the GNUstep project. By Adam Fedor.
- http://www.gnustep.org/resources/ObjCFun.html

Objective-C
- At the Portland Pattern Repository Wiki.
- http://c2.com/cgi/wiki?ObjectiveCee

comp.lang.objective-c FAQ
- Frequently asked questions about Objective-C.
- ftp://rtfm.mit.edu/pub/faqs/computer-lang/Objective-C/faq

Objective-C Resources
- Directory Objective-C resources.
- http://www.foldr.org/~michaelw/objective-c/

A First Look at Objective-C
- Article by Noah Roberts.
- http://www.gmonline.demon.co.uk/cscene/CS7/CS7-05.html

Optimizing Objective-C Code
- Articles and samples to help you get maximum performance from your Objective-C code.
- http://www.mulle-kybernetik.com/artikel/Optimization/opti.html

Programming: Objective-C
- Includes tutorials, reference material and downloads.
- http://www.toodarkpark.org/computers/programs/objc.html

Programming in Objective-C
- Some introductory notes and examples of Objective-C.
- http://www.cs.indiana.edu/classes/c304/oop-intro.html

Cetus Links - Objective-C
- Links on Objects, Components and Objective-C. Provides links on tutorial, newsletter, books, software and libraries.
- http://www.cetus-links.org/oo_objective_c.html