There are a lot of active Twitter users who use Swift; in many cases, posts will be marked with the #swift hashtag and can be found at http://twitter.com/search?q=%23swift. Popular users that the author follows include (in an alphabetical order of their Twitter handle names):
@AirspeedSwift: A good selection of tweets and re-tweets of Swift-related subjects@ChrisEidhof: The author of the Functional Swift book and@objcio@CodeWithChris: A collection of tutorials on iOS programming@CodingInSwift: Crossposts by a collection of Swift resources@cwagdev: Chris Wagner writes some of the iOS tutorials with Ray Wenderlich@FunctionalSwift: A selection of functional snippets along with a Functional Swift book@NatashaTheRobot: A great summary of what's happening along with newsletters and cross references@nnnnnnnn: Nate Cook, who reviewed this book and provides the Swifter list above@PracticalSwift: A good collection of blog posts that talk about the Swift language@rwenderlich: Ray Wenderlich has many posts related to iOS development, a wealth of information, and more recently Swift topics as well@SwiftLDN: Swift meetups based in London, who also invite great Swift talks and presenters
In addition to the Swift-focused Twitter users, there are a number of other Cocoa (Objective-C) developers who blog regularly on topics related to the iOS and OSX platforms. Given that any Objective-C framework can be integrated into a Swift app (and vice versa), quite often there will be useful information that you can get by reading these posts:
@Cocoanetics: Oliver Drobnik writes about iOS and provides training@CocoaPods: CocoaPods is a dependency management system for Objective-C frameworks (pods) and is being extended into the Swift domain@Mattt: Matt Thompson writes about many iOS subjects and is the author of the AFNetworking and Alamofire networking libraries@MikeAbdullah: Mike Abdullah writes about general iOS development@MikeAsh: Mike Ash knows everything there is to know, and for what he doesn't know, he finds out@MZarra: Marcus S Zarra has written a lot about Core Data and syncing@NSHipster: A collection of assembled iOS and Cocoa posts, organized by Matt Thompson@objcio: A monthly publication on Objective-C topics, with some Swift@PerlMunger: Matt Long posts about Swift, Cocoa, and iOS
The reviewers of this book are:
@AnilVrgs: Anil Varghese@ArvidGerstmann: Arvid Gerstmann@jiaaro: James Robert@nnnnnnnn: Nate Cook
The author's personal and book twitter accounts are:
@AlBlue: The author's twitter account@SwiftEssentials: The book's twitter account
Meetups such as @SwiftLdn keep a track of interesting Swift writers in a Twitter list at https://twitter.com/SwiftLDN/lists/swift-writers/members, which might have more up-to-date recommendations than this section, as well as of the Ray Wenderlich team at https://twitter.com/rwenderlich/lists/raywenderlich-com-team/members.