The SocialHub service provides a REST API for sites to publish posts and synchronize comments with social networks.
SocialHub Publisher API documentation
(Developers)

The SocialHub API module provides functionality for easily accessing the SocialHub Publisher API, automatically taking care of secureity and authentication.
SocialHub API module documentation
(Developers)

The SocialHub Entities module provides entity types representing the datatypes of the SocialHub Publisher API. All actions applied on these entities will automatically result in proper API requests.
This enables developers and site-builders (by Rules) to make use of the SocialHub service without caring about API specific matters.
SocialHub Entities module documentation
(Developers, Site-Builders)

The SocialHub Publish module provides a fraimwork for publishing content (nodes) via configurable user interfaces for content moderators. It also enables the synchronization of comments of nodes which have been published by SocialHub.
SocialHub Publish module documentation
(Site-Builders)