To access the LinkedIn API via iOS, Hisham Raslan offers a library that aims user simplification via Auth2.0. Steps include to follow LinkedIn developer instructions to add an application, select appropriate permissions, and use APIkey/secret key to download the library.
Facebook has updated the Facebook SDK 3.1 for iOS, adding the ability to integrate Facebook in iOS 6 as well as other new features. Apple has added several new native features in iOS 6 including Auth dialog and view controller (share dialog). The Facebook SDK supports the use of these APIs.
Facebook recently introduced Graph API V3.2, which includes updates to Instagram Graph API, Page Insights, Pages and Video Polls, and Marketing API. The company also announced updates to Facebook Login and the Messenger App.