Links

iOS Development

Swift API GuidelinesSwift API Guidelines
Krzysztof Zabłocki's BlogGreat resource for app architecture
John Sundell's BlogNice blog about Swift by John
Ray WenderlichLots of tutorials for iOS, macOS, tvOS, watchOS, etc.
iOS Support MatrixNice overview of iOS devices and iOS compatibility
fastlaneAmazing app automation toolset
Blake's iOS Device Specifications GridNice overview of iOS device hardware specs
The Ultimate Guide To iPhone ResolutionsAll about iPhone resolutions
Interface Builder Tips and TricksSome neat tricks for Interface Builder
PaintCodeTurn drawings into Swift code
PawHTTP client for REST API development
DashAPI Documentation Browser
Hopper DisassemblerDisassemble, decompile and debug your applications

Programming

Dictionary of Algorithms and Data StructuresIn case you want to look up an algorithm...
jfdube's Blogjfdube is Technical Architect at Ubisoft Montreal
Stack OverflowThe definitve site for all kind of programming questions
Sutter's MillHerb Sutter is one of the leading authorities in C++ Development

Tools / Engines / Libraries

Unity 3DGreat engine for smaller games or prototyping
Unreal Engine 4Cutting Edge Game Engine

General

Khan AcademyIt was never easier to learn stuff...
TEDGreat people sharing great ideas