SwapKit is a library to allow locally installed iPhone apps to share data among themselves. It supplies facilities iPhone OS does not provide, including shared metadata on installed apps, binding applications to data types and app capabilities (similar to how apps in desktop OSes bind themselves to file types), and providing one-way and (planned) two-way communication to let apps collaborate and do more than any single one could ever hope to.

InAppSettings is an open source iPhone and iPod touch framework for displaying an in app version of the settings from the Settings.bundle.

A library for testing resolution-independent iPhone OS applications.

ResKit simulates varying device screen sizes by resizing and moving your application's main window. It supports scaling down the simulated device so more of the screen can be seen at once.

CoverFlow API replacement for the iPhone

UITableViewCell subclass that adds a badgeNumber (int) property the cell. This badge draws in an identical manner to the badges present in MobileMail.app. The class supports custom badge colours for both normal and highlighted states.

ZSync is an open source syncing library designed to allow easy syncing of data between an iPhone/iPod Touch and the OS X Desktop. ZSync utilizes the BLIP library and Apple’s Sync Services to allow easy and seamless syncing of data.