RestKit
Framework for consuming and modeling RESTful web resources
...It provides a powerful object mapping engine that seamlessly integrates with Core Data and a simple set of networking primitives for mapping HTTP requests and responses built on top of AFNetworking. It has an elegant, carefully designed set of APIs that make accessing and modeling RESTful resources feel almost magical. You can even access the Twitter public timeline and turn the JSON contents into an array of Tweet objects. RestKit is designed to be modular and each module strives to maintain a minimal set of dependencies across the framework and with the host platform. At the core of library sits the object mapping engine, which is responsible for transforming objects between representations (such as JSON/XML <-> local domain objects). ...