Link Sites

Apple Developer Sites 

This is the main site for Apple Developer - https://developer.apple.com/

This is the main site for iOS Development - https://developer.apple.com/ios/

This is the main site for Swift Programming - https://developer.apple.com/swift/

To engage discussion with other Apple developer you can join the Apple Developer Forum - https://forums.developer.apple.com/welcome

To watch various video about Apple technologies please go to - https://developer.apple.com/videos/

Apple Developer Member

To register as Apple developer, select "Member Center" from any site above. Registration is free. The benefit is that you can download beta version of Xcode and iOS for testing.

If you want to publish your app to the app store, you need to enrol for the Apple Developer Program. You can do it in the "Member Center".

Swift Programming Resource - Apple Site

This is the main resource site for Swift programming - https://developer.apple.com/swift/resources/

You can download the latest Xcode beta at the link below for free.  https://developer.apple.com/xcode/download/
For official release of Xcode, I recommend using App Store to download.

Swift Programming Guide

The link below is where you can find the official Swift Programming Guide https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/index.html. You can also download this book via iBook store for free.

For Swift standard library, you can check out  https://developer.apple.com/library/ios//documentation/General/Reference/SwiftStandardLibraryReference/index.html

The following site "Start Developing iOS App" will help you get your feet wet by introducing the basics of Swift programming and iOS development using an example. https://developer.apple.com/library/ios/referencelibrary/GettingStarted/DevelopiOSAppsSwift/index.html

The following is the online guide to "Using Swift with Cocoa and Objective-C". You can also download this book via iBook store for free. https://developer.apple.com/library/ios/documentation/Swift/Conceptual/BuildingCocoaApps/index.html

iOS Developer Library

You can access iOS Developer Library at https://developer.apple.com/library/ios/navigation/. All types of documentation about the iOS development documentation are located here.

Open Source Swift

Since Swift is now open source, you can access and participate in the open source community via Swift.org