Embarking upon iPhone development is a daunting prospect. The Apple iPhone Developer area is huge, the SDK is massive and one can't help but wonder where to start.
Fortunately there are some superb resources to help guide you on your way.
My journey started at Lynda.com where you will find several hours of superb lessons right from the basics to developing your first applications. Rather than buy a book, spend $25 on a months subscription here. It covers a lot of the core principals of objective c++ in a non heavy way and leads you by the hand through the X Code tools you need to develop apps.
My Code Teacher is a new paid tutorial site with a course on iPhone Development. I have not viewed the videos yet but there is a free hello world video http://mycodeteacher.com/freelessons.php
Another great find was http://appsamuck.com/ where there are 31 days of tutorials and 31 saple iPhone apps to build via text based guides with the finished apps as zip files too. A lot more simplisticly presented but good in depth content and broad subjects. Please note the code samples are SDK 2 which show just how fast things are moving.