The Accounts framework provides access to user accounts stored in the Accounts database. An account stores the login credentials of a particular service, such as Twitter, that can be used as authentication for the service. By implementing the Accounts framework into your app, you do not need to be responsible for storing account logins yourself. Instead, the user can grant access for your app to use their account login credentials, bypassing the need to type their username and password. If no account for a particular service exists in the user’s Accounts database, you can let them create and save an account from within your app.

The Address Book framework provides access to a centralized contacts database, called the Address Book database, that stores a user’s contacts. Applications such as Mail and Messages use this database to present information about known and unknown persons.

The Address Book UI framework provides controllers that facilitate displaying, editing, selecting, and creating records in the Address Book database.

The Ad Support framework provides apps with access to an identifier that can be used only for serving advertisements, as well as a flag which indicates whether a user has limited ad tracking. Accessing the advertising identifier requires apps to read and honor the opt-out flag.

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In iOS and OS X, the Photos framework (formerly known as Assets Library framework) provides classes that support building photo editing extensions for the Photos app. In iOS, the Photos framework also provides direct access to the photo and video assets managed by the Photos app, including the iCloud Photo Library. Use this framework to retrieve assets for display and playback, edit their image or video content, or work with collections of assets such as albums, moments, and iCloud Shared Albums.

Functional programming constructs for Objective-C collections (map, reduce, each, filter, inject).

The AV Foundation framework provides an Objective-C interface for managing and playing audio-visual media in iOS and OS X applications.

ChartboostSDK for showing ads and more.

cocos2d for iPhone is a framework for building 2D games