The Appboy .NET SDK by Marcel Bradea allows communication with the API to implement marketing automation features into mobile applications. Resources include object model, data integrity, and error handling.
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.
Schoology, a collaborative learning platform that is 100% cloud-based, has recently announced the launch of the Schoology App Center which features third-party applications built with the Schoology API and developer platform. Using the Schoology API, developers can build applications that extend features and functionality as well as build applications that run directly in the Schoology platform.