Really useful little project by Nick Lockwood, by specifying that a SUBCLASS_MUST_OVERRIDE in a method, the app will crash on startup which is much better than having to wait until the method is actually called.
Fantastic collection of Swift resources by Matteo Crippa. I hadn't come across this before but it turns out it's a standard format which has been around for a while. You might also be interested in Awesome iOS or the other two Swift repositories (1, 2). It'd be great to see all of the Swift ones consolidated into one.
Nate Cook (who's doing a great job taking over from Mattt at NSHipster) on collection types in Swift. It's interesting to look at how quickly his SortedCollection class comes together by simply implementing the various collection protocols.