BlocksKit was started by Zachary Waldowski and later I joined the project. It aims to add block-based helpers to otherwise more difficult tasks in Objective-C, both in iOS and OS X projects.
Blocks in C and Objective-C are downright magical. They make coding easier and potentially quicker, not to mention faster on the front end with multithreading and Grand Central Dispatch. BlocksKit hopes to facilitate this kind of programming by removing some of the annoying - and, in some cases, impeding - limits on coding with blocks.
BlocksKit is a framework for OS X Mountain Lion and newer and a static library for iOS 6 and newer.