http://www.anysim.net
http://www.bmw-eba.de.tl

There are varying philosophies on how to learn anything, and I am surprised by many of the avenues suggested. I must be thick-headed or just plain stupid, but I do not recommend starting right off with Objective C and/or Cocoa without an understanding of C. I have some experience in scripting with a C based language and have written many gui based software tools. Into just the 3rd chapter of the Cocoa book I was lost. Objective C is very different. The syntax is different, the workflow is different, and it is a higher level of abstraction than C. If you do not understand the basic rules, logic, memory management, and abstraction of data that is entailed in C, you will be hard-pressed to really understand what is going on with Objective C.

Many instruction books use the tutorial method of teaching, which I like, but that does not provide you with the real understanding of what you are doing. “Push this button, enter this code, type this command, now compile it. Congratulations, you have just written an application! You are a programmer.”
Most books assume a prior knowledge, and even if they don’t they still speak to you as an engineer, using unfamiliar terms and concepts, and not distilling the abstract down to the most basic common sense ideas.
The K.N. King C book is an exception. That is why I recommend it.

Just briefly browsing through the Apple documentation of Cocoa and the associated libraries convinced me that this is a daunting task. I have chosen to start at the beginning, because I want to really understand what I am doing, not just mimic what I saw in a tutorial.