I am starting my journey with Swift programming. Although, over the past few years I have dabbled a little with objective C programming and iOS. Just recently, I came across a university taught course on Mobile programming with Swift.
This course starts out with a reading assignment - Apple's Introduction to Swift. Before I get started, I want to touch on that I am in Apple's developer program. This now includes resources for Mac OSX, iOS, and WatchOS. I am going to upgrade to latest version of Xcode before i get started. On the downloads page I can find they have Xcode 7 beta available which I will try out. They talk about the features including Interface Builder on the Xcode page. As well, the Swift now is at version 2.
Apple in 2004 released a book on Swift Programming Language. One more resource I came across is free book on basics from ibooks store from apple. The corresponding web site is http://swiftcenter.net/ . Lastly, an ebook on Swift you can buy.