Objective-C cheat sheet [closed]

Answer 1

Here is another cheat sheet which compares C, C++, Objective-C and C#. Useful if you're coming from one of the other "C-like" languages.

Platform Languages: C, C++, Objective C, Java, C# a side-by-side reference sheet

Answer 2

The Apple developer site has Introduction to The Objective-C 2.0 Programming Language (dead link)

A 10-Minute Introduction to Objective-C

The Ultimate iPhone Objective-C Cheat Sheet

Objective-C Cheat Sheet (dead link)

Objective-C Cheat Sheet (pdf) (dead link)