iPhone 101
Code Tips
Resources
Links
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I'm working on some iPhone 101 material for this site; if you'd like to be notified when it's ready, subscribe to the newsfeed or follow me on twitter.
Meanwhile, here are some resources I recommend to get you started:
Get a book.
There are several books out now for iPhone development; I'd recommend Beginning iPhone Development: Exploring the iPhone SDK. It'll show you how to add different UI elements, handle user input, save (and load) data, detect touches, taps and swipes, use the location manager to see where you are, use the accelerometer to detect motion, and lots more.
If you've never done programming before, you may also want to pick up
Programming in Objective-C 2.0
Also, the folks over at Pragmatic Programmers have an iPhone book on the way; it's available now in ebook format.
Take a class.
Stanford University's iPhone Application Programming course is available online. The lectures can be downloaded from iTunes, and the assignments are available online.
Big Nerd Ranch offers several iPhone development classes which take you from novice to iPhone developer in just 7 days. (For best results, however, you should be familiar with some other programming language, or work through the Objective-C book before going to the class.) Class tuition includes room and board for the week.
Pragmatic Studio (from Pragmatic Programmers) offers iPhone SDK training classes. Upcoming classes are in Reston VA and Denver CO.
Mobile Orchard is offering Beginning iPhone Programming classes in the Bay Area and Seattle. These classes are for programmers experienced in other languages.
Read the Apple Docco.
There's a ton of information, documentation and examples on the Apple site. Here are some to get you started:
Visit Apple's iPhone Developer Site for more documentation.
Jump in and start hacking.
The best way to learn is by doing. Figure out what you want your app to do, and start building it. You can refer to Apple's sample code for ideas; also check out the code on this site for examples. If you get stuck, ask for help on the iPhone Programming Forums on MacRumors, or on Apple's iPhone Developer Forums. And don't forget about Google; you can search for the thing you're trying to code, or the bug you're trying to debug, and turn up lots of useful info.
Good luck!