Download
WD Basics!
Making apps will be a lot easier if you already have some practice time in web development.
Download Web Design Basics for iPad to learn basic web design coding.
Do you want to program for the iPad or iPhone/iPod Touch, or both? You need to buy them and immerse yourself in them. Carry them with you. Try apps. Try apps with good reviews, try apps with bad reviews. Read magazines on them. Talk to your friends about apps. Listen for needs. What could the device do that it doesn't do yet?
You have to decide if you want to develop for web or native. Native is the type of app that is sold in the App Store. Web apps can be written in HTML5/CSS3/JavaScript. Each has its plus and minuses, but this page generally focuses on native apps for the App Store.
Developing native apps require that you Purchase an Intel Mac. Personally I think Macs are awesomely terrific, but the cost could force you to start in web apps, then move to native apps later.
If you're developing native apps for the App Store, you're going to need to know how to program. The following books should really help you out. Two of them are on my absolute must list, but they're thick so they might not be your first jump.
For those just starting out, I recommend these books
And these specific books