Below are some Apple references materials that I follow when starting out iphone dev sometime ago. It's more or less in order of reading from the introductory/basic to specific :
- IOS First App. Useful to get the feel of the overall development.
- Objective-C Programming Language
- Cocoa Fundamental Guide. Explore the main/core Framework being used in iOS development.
- iOS App Programing Guide. Discuss things like how the program actually execute on the device and how it relate to the code.
- Tools Workflow Guide for iOS. Discuss things like the deployment to device, testing, etc..
- XCode4 User Guide, Getting familiar more with the IDE would help a lot in day to day programming
- iOS Human Interface Guidelines. Some guidelines on GUI component usage and conventions.