These are social APIs we're using to understand what social APIs do.
Social Network APIs
These are APIs that support a social network model. That is, users can friend or follow each other, and receive updates of others' activities or content.
- pump.io API
- StatusNet AtomPub API
- OpenSocial Activity Streams API
- Twitter API
- Facebook API groups, events, pages (places, ...)
- Google+ API
- Foursquare API places
- Flickr API photos, albums
- Github API projects, organizations
- Meetup API - No direct connections between users, but users can join groups or events
- Trello API projects, organizations
- Stackexchange API
- IBM Connections API
- Yammer API
- Socialcast API
- TIBCO tibbr API
- Mixi API
These are APIs that don't use a social networking model.