I currently subscribe to Venmo's style guide.
Xib
I lean heavily on xibs in order to build views that are self contained but that can still be created with interface builder. Here is a YouTube video I made on working with xib files from .storyboard: https://www.youtube.com/watch?v=H-55qZYc9qI. Written article coming soon.
Protocol Oriented Programming
Among the more exciting new features [of Swift] are protocol extensions. In the first version of Swift, it was possible to extend the functionality of existing class, struct and enum types. Now with Swift 2, you can extend a protocol as well.
Here is an article from raywenderlich.com discussing some protocol features.
I also really liked Apple's video on protocol oriented programming from WWDC 2015.
Further Readings
Here is a list of articles that I find particularly good: - Tuples, Protocols, Delegates, and Table Views - Getting to Know Enums, Structs and Classes in Swift - Swift Cheat Sheet and Quick Reference - Reference vs Value Types in Swift - Introducing iOS Design Patterns in Swift - Instruments Tutorial with Swift - Unit Testing Tutorial: Mocking Objects