The definitive guide to the language. A lot of material to consume here, but the best place to start.
Build your own Tetris clone in Swift, complete with annoying Tetris noises. Fun!
Resources created by https://codepath.com, an excellent training program for experienced developers based in San Francisco.
Security resources for app developers
Natasha writes great articles about Swift.
Mattt is an excellent writer and presenter; anything he publishes is well worth consuming.
I'm a long-time fan, and recommend you buy a subscription. Episodes are short, great for those of us with brief attention spans.
The classic choice for learning iOS-related APIs and languages.
How do existing patterns from Objective C translate to Swift ?
These are the best resources (aimed at professional developers) I've found whilst learning Swift. Have others that should be included on this list ? Tweet me @gemmakbarlow.