Creating a Universal Apps
http://developer.apple.com/library/ios/#documentation/iPhone/Conceptual/
iPhoneOSProgrammingGuide/AdvancedAppTricks/AdvancedAppTricks.html

iPad Apps Sample Code
http://developer.apple.com/library/ios/navigation/#section=Resource%20Types&topic=Sample%20Code

Start Developing iPad Apps
http://developer.apple.com/ipad/sdk/