Audio

• AudioKit - Audio synthesis, processing, and analysis platform
• MusicKit - Framework and DSL for creating, analyzing, and transforming music in Swift
• FluidAudio - On-device speech processing for iOS and macOS: ASR, TTS, VAD, and speaker diarization

Caching

• HanekeSwift - A lightweight generic cache for iOS written in Swift with extra love for images.
• Carlos - A simple but flexible cache for iOS and WatchOS 2 apps, written in Swift.

Command Line

• CommandCougar - An elegant pure Swift library for building command line applications.

Databases

• SQLite.swift - A pure Swift framework wrapping SQLite3. Small. Simple. Safe.
• SwiftMongoDB - A Swift driver for MongoDB.
• ModelAssistant - Elegant library to manage the interactions between view and model in Swift.
• SwiftData - A simple and effective wrapper around the SQLite3 C API written completely in Swift.
• Squeal - A Swift wrapper for SQLite databases.
• SQLiteDB - Basic SQLite wrapper for Swift.
• PostgresClientKit - A PostgreSQL client library for Swift. Does not require libpq.
• Realm - A mobile database that runs directly inside phones, tablets or wearables.

Documentation

• jazzy - A soulful way to generate docs for Swift & Objective-C

Events

• Caravel - A Swift event bus for UIWebView and JS
• EmitterKit - An elegant event framework built in Swift
• Swift-Custom-Events - A very simple way to implement Backbone.js style custom event listeners and triggering in Swift for iOS development.
• Kugel - A glorious Swift wrapper around NSNotificationCenter

Extensions

• PromiseKit - A delightful Promises implementation for iOS.
• Promise - Simple promises library in Swift.
• SwiftTask - Promise + progress + pause + cancel, using SwiftState (state machine).
• Pythonic.swift - Pythonic tool-belt for Swift – a Swift implementation of selected parts of Python standard library.
• Euler - Swift Custom Operators for Mathematical Notation.
• AlecrimCoreData - A simple Core Data wrapper library written in Swift.
• Async - Syntactic sugar in Swift for asynchronous dispatches in Grand Central Dispatch.
• LlamaKit - Collection of must-have functional Swift tools.
• Pluralize.swift - Great Swift String Pluralize Extension
• BrightFutures - Write great asynchronous code in Swift using futures and promises.
• BFKit-Swift - A collection of useful classes to develop Apps faster.
• Sugar - Something sweet that goes great with your Cocoa.
• Bow - Companion library for Typed Functional Programming in Swift.
• SwiftCoroutine - Swift coroutines for iOS and macOS.
• ExSwift - JavaScript (Lo-Dash, Underscore) & Ruby inspired set of Swift extensions for standard types and classes.
• Observable-Swift - Value Observing and Events for Swift.
• Promissum - Promise library with functional combinators like map, flatMap, whenAll & whenAny.
• PureFutures - Futures and Promises library
• SWRoute - A tiny Swift wrapper. Allows you to route (hook) quite any function/method with another function/method or even a closure.
• Easy-Cal-Swift - Overload +-*/ operator for Swift, make it easier to use (and not so strict).
• ReactKit - Swift Reactive Programming.
• Basis - A number of foundational functions, types, and typeclasses.
• CAAnimation + Closure - Add start / completion closures for CAAnimation instances
• SwiftSequence - A μframework of extensions for SequenceType in Swift 2.0, inspired by Python's itertools, Haskell's standard library, and other things.
• EZSwiftExtensions - 😏 How Swift standard types and classes were supposed to work.
• SwiftyUserDefaults
• ZamzamKit - A collection of micro utilities and extensions for Standard Library, Foundation and UIKit.
• swix - Swift Matrix and Machine Learning Library.

HTTP

• Alamofire - an HTTP networking library written in Swift.
• ReactiveAPI - Write clean, concise and declarative network code relying on URLSession, with the power of RxSwift. Inspired by Retrofit.
• SwiftHTTP - Thin wrapper around NSURLSession in swift. Simplifies HTTP requests.
• SwiftWebSocket - High performance WebSocket client library for Swift.
• Nuke - Advanced framework for loading and caching images
• Taylor - a web server library in Swift.
• Perfect - a web framework tayin Swift.
• Kingfisher - A lightweight and pure Swift implemented library for downloading and caching image from the web.
• Net - HttpRequest wrapper written in Swift.
• SocketIO-Kit - Socket.io iOS/OSX Client compatible with v1.0 and later
• Siesta - Ends state headaches by providing a resource-centric alternative to the familiar request-centric approach to HTTP.
• Just - HTTP for Humans (python-requests style HTTP library)

JSON/XML Manipulation

• SwiftyJSON - The better way to deal with JSON data in Swift.
• Argo - JSON parsing library for Swift, inspired by Aeson.
• SWXMLHash - Simple XML parsing in Swift.
• AEXML - Simple and lightweight XML parser for iOS written in Swift.
• JASON - JSON parsing with outstanding performances and convenient operators.
• Fuzi - A fast & lightweight XML/HTML parser with XPath & CSS support in Swift 2.
• SwiftyJSONAccelerator - Generate Swift 5 model files from JSON with Codeable support.
• json-swift - A basic library for working with JSON in Swift.
• Alamofire-SwiftyJSON - Alamofire extension for serialize NSData to SwiftyJSON.
• Starscream - WebSockets Library
• Tailor - A super fast & convenient object mapper tailored for your needs.
• ObjectMapper - JSON Object mapping written in Swift.

Logging

• CleanroomLogger - A configurable and extensible pure Swift logging API that is simple, lightweight and performant.
• XCGLogger - A debug log framework for use in Swift projects.
• Log - A logging tool with built-in themes, formatters, and a nice API to define your owns.
• NSLogger - A high perfomance logging utility which displays traces emitted by client applications running on Mac OS X, iOS and Android.
• Swell - A logging utility for Swift and Objective C.
• QorumLogs

Misc

• SwiftKVC - Key-Value Coding (KVC) for native Swift classes and structs
• Tactile - A safer and more idiomatic way to respond to gestures and control events.
• SwiftValidators - String validation for iOS developed in Swift. Inspired by validator.js
• acli - commandline tool to download curated libraries from github (very beta)
• Compass - Compass helps you setup a central navigation system for your application.
• Versions - Helping you find inner peace when comparing version numbers in Swift

Queue

• GCDKit - Grand Central Dispatch simplified with Swift.
• TaskQueue - A Task Queue Class developed in Swift.
• Dispatcher - Queues, timers, and task groups in Swift

Security

• CryptoSwift - Crypto related functions and helpers for Swift implemented in Swift programming language.
• SwiftyRSA - RSA public/private key encryption in Swift
• SHA256-Swift - Swift framework wrapping CommonCrypto's SHA256 methods.
• SwiftSSL - An Elegant crypto toolkit in Swift.

Swift Books

• Using Swift with Cocoa and Objective-C
• Learn to Program iOS and OS X with Apple Swift
• Swift Standard Library Reference

Swift Playgrounds

• Learn-swift playground - Learn Swift interactively through these playgrounds.
• awesome-awesomeness
• Design-Patterns-In-Swift - Design Patterns implemented in Swift.
• SwiftStub - an online Swift playground and REPL.

Swift Videos

• TheSwiftLanguage youtube channel - Videos about the Swift programming language by Apple.
• Developing iOS 8 Apps with Swift - Stanford course by Paul Hegarty.

Swift Websites

• Swift Collection on Medium - Collection of blog posts about Swift on Medium.
• Natasha The Robot - Nice blog about Swift by Natasha The Robot.
• Hacking with Swift - a complete Swift training course that teaches you app development through 36 hands-on projects, for free.
• WWDC-Recap - A collection of session summaries in markdown format, from WWDC 19 & 17.
• Cocoacasts - Tutorials and videos about Swift and Cocoa development.
• We ❤ Swift - Tutorials and guides.
• Jameson Quave's blog - Tips for everyday work with Swift.
• SwiftInFlux - An attempt to gather all that is in flux in Swift.
• Official website - A home page of Swift programming language.
• Swift Collection on raywenderlich.com - Collection of blog posts about Swift on raywenderlich.
• SwiftLang - a Swift Resource Center & Community.

Testing

• Quick - A behavior-driven development test framework for Swift and Objective-C.
• Sleipnir - A BDD-style framework for Swift.
• Nimble - A Matcher Framework for Swift.
• Fakery - Swift fake data generator.
• SwiftRandom - Generator for random data.
• MockFive - A mocking framework for Swift with runtime function stubbing.

Third Party APIs

• Swifter - A Twitter framework for iOS & OS X written in Swift
• GooglePlacesAutocomplete - Simple Google Places address entry for iOS.
• SwiftIB - An InteractiveBrokers API Library for OS X written in Swift. InteractiveBrokers is one of a few, if not the best, brokerage company provide Gateway+API solution for traders.

UI

• Sejima - User Interface Library components for iOS.
• Eureka - Elegant iOS Forms in pure Swift.
• XLActionController - Fully customizable and extensible action sheet controller written in Swift.
• FontAwesome.swift - Use FontAwesome in your Swift projects.
• SwiftOverlays - GUI library for displaying various popups and notifications.
• TagCellLayout - UICollectionView layout for Tags with Left, Center & Right alignments.
• SwiftyButton - Simple and customizable button in Swift
• Swiftstraints - Powerful auto-layout framework that lets you write constraints in one line of code.
• GaugeKit - Customizable gauges. Easy reproduce Apple's style gauges.
• Hokusai - A library for a cool bouncy action sheet
• LNRSimpleNotifications - Simple Swift in-app notifications
• GoogleMaterialIconFont - Google Material Icon Font for Swift and ObjC.
• EZAlertController - Easy Swift UIAlertController
• Notie - In-app notification in Swift, with customizable buttons and input text field.
• HTYTextField - A UITextField with bouncy placeholder in Swift.
• SlideMenuControllerSwift - iOS Slide Menu View based on Google+, iQON, Feedly, Ameba iOS app. It is written in pure swift.
• SimpleAlert - Customizable simple Alert and simple ActionSheet for Swift
• Interactive Side Menu - Customizable iOS Interactive Side Menu written in Swift 3.0.
• NFDownloadButton - Revamped Download Button.
• EFQRCode - A better way to operate quick response code in Swift.
• SendIndicator - Yet another task indicator.
• SectionedSlider - Control Center Slider.
• Cupcake - An easy way to create and layout UI components for iOS.
• Gemini - Gemini is rich scroll based animation framework for iOS, written in Swift.
• Hero - Hero is a library for building iOS view controller transitions.
• Ribbon - 🎀 A simple cross-platform toolbar/custom input accessory view library for iOS & macOS.
• PagingMenuController - Paging view controller with customizable menu in Swift
• ImagePicker - A nicely designed and super easy to use ImagePicker. 📷
• Whisper - Break the silence of your UI, whispering, shouting or whistling at it
• SwiftPasscodeLock - An iOS passcode lock with TouchID authentication written in Swift.
• PinLayout - Extremely Fast views layouting without auto layout. No magic, pure code, full control and blazing fast. Concise syntax, intuitive, readable & chainable.
• CrispyCalendar - CrispyCalendar is the calendar UI framework.
• Hue - Hue is the all-in-one coloring utility that you'll ever need.
• SAHistoryNavigationViewController - SAHistoryNavigationViewController realizes iOS task manager like UI in UINavigationContoller.
• ios-charts - A powerful chart / graph framework, the iOS equivalent to MPAndroidChart.
• TagListView - Simple but highly customizable iOS tag list view.
• WobbleView - Implementation of wobble effect for any view in app.