I wish this page had been available when I started iPhone development. Its a nice 50,000 foot description of the basics for someone who is a developer, but is new to Apple development.
But be careful, while its a good intro, there are mistakes and things not explained as clearly as they should be. For example the dot-notation to access instance variables comment. This is "kinda true" but not strictly accurate, the dot-notation is short hand for calling the getter and setter methods of the instance variables, it doesn't access the instance variables directly.
(Matt Legend Gemmell - iPhone Development Emergency Guide)