The Facebook Messenger Platform Python SDK by egalicia allows developers to integrate the Facebook Messenger Platform APIs into their Python applications. The documentation for this SDK is given in Spanish.
A brand new iOS messaging/social app called Peach has rocketed in popularity since launching last Friday. A developer has reverse engineered the Peach API and created clients for Swift and Mac. The clients have been posted on GitHub for developers interested in using the undocumented Peach API.
Gowalla, the location aware social networking service, has announced the release of their first public API (our Gowalla API profile). This will help them keep up with other location-centric social services like Foursquare's new API.