TripAdvisor Facebook Android SDK by TripAdvisor. Allows to integrate travel functionalities into Facebook applications with the aim to engage users socially. Includes documentation to login, sharing, AppLinks, and Graph API. Authored by Kedar Sarmalkar. For more information, visit https://developers.facebook.com/docs/android
A project of the Elgg Foundation, Elgg is a free open source social networking engine licensed to users under the GNU Public License v2. The REST Elgg API allows developers to integrate Elgg and offer new apps for it. To give a sense of its size, 1,646 plugins have been created so far by the user community, with nearly 3 million downloads. Examples of plugins include blogs, forums, social bookmarks.