iOS

Websites

Main developer website: https://developer.apple.com/devcenter/ios/index.action

Developer library: https://developer.apple.com/library/ios/navigation/#

HIG: http://developer.apple.com/library/ios/#documentation/UserExperience/Conceptual/MobileHIG/Introduction/Introduction.html

Tools

Xcode

Guides

Start developing iOS apps today: https://developer.apple.com/library/ios/#referencelibrary/GettingStarted/RoadMapiOS/chapters/Introduction.html

Your first iOS app: https://developer.apple.com/library/ios/#referencelibrary/GettingStarted/RoadMapiOS/chapters/RM_YourFirstApp_iOS/Articles/00_Introduction.html