iPhone development is the forefront of "cool" programming. Doing something with your latest toy and potentially selling it to millions of people, making a few bucks along the way. The main stumbling block (assuming you have a Mac) is the Objective-C language.
My experience in programming starts out with Java (university) -> PHP -> C# -> ASP .NET. Nowhere along the way have I ever delt with memory management or pointers. However, you can pick these things up quite quickly once you've had some things explained to you. So, here's 10 great sites for starting out in your iPhone development.
Stanford Cocoa Programming Course
A full 20-lecture course with sample code, walkthrough assignments and guest lectures from Apple employees. If you've ever been through uni/college you'll know what to expect, a bit of a challenge to the casual developer but you'll learn amazingly quickly. Thoroughly recommended.
Apple Developer Documentation
The bible for iPhone developers. The whole SDK can be viewed from here along with some great exercises and videos on how the whole thing works. When you download the SDK you can download this whole library into XCode for viewing offline.
A Digg-esque site for bookmarking iPhone resources. Not a massive community at the moment but it's getting there.
Jeff LaMarche's Blog
Jeff has been an Objective-C programmer for the past 10 years and regularly blogs about iPhone development, whether it's a new component or some funky OpenGL particle system. His posts are full of great code samples so go have a look!
Tim Haines' Twitter List
If you're in to Twitter (like I am) Tim Haines maintains a list of iPhone developers on Twitter. If you go and put your name on the spreadsheet there's a ruby script you can run to follow all the developers on that list. You'll get access to hundreds of people-worth of knowledge and help. The community is very friendly and always willing to help you out.
So, good luck making your shiny new app! If you have any good sites you want added to the list, leave a comment!