STTwitter is a stable, mature and comprehensive Objective-C library for Twitter REST API 1. STTwitter is like a FOSS version of Twitter Fabric TwitterKit, without the UI parts but with much more flexibility. It can be easily adapted into a project by dragging and dropping all related documents.
SwiftyUserDefaults makes user defaults enjoyable to use by combining expressive Swifty API with the benefits of static typing. SwiftyUserDefaults defines your keys in one place, use value types easily, and get extra safety and convenient compile-time checks for free.
TITokenField is an iOSversion of the NSTokenField (See To: field in Mail and Messages). TITokenField is limited at the moment to one tokenising field and a content view below because it's pulled straight from one of my apps. Multiple field support also require tweaking.
Transition Kit is an Objective-C library for elegantly implementing state machines. Transition Kit is full-featured, completely documented, and very thoroughly unit tested. State machines are a great way to manage complexity in your application and TransitionKit provides you with an elegant API for implementing state machines in your next iOSor Mac OS X application.
UAFilterableResultsController is an implementation of a NSFetchedResultsController-style pattern using NSMutableArray as the backing store instead of Core Data. UAFilterableResultsController provides methods for manipulation and filtering of the store.