The Untappd Ruby SDK by Chris Mar wraps the API to access beers, breweries,and bars features with the aim to implement in social applications. Guides available on GitHub include Api Key, documentation, parameters, methods, and responses.
Keek, social video network, recently announced the release of the Keek API. Alongside the API launch, Keek established a developer portal that includes tools and resources to assist developers in integrating Keek with third party applications. The Keek API grants developers access to public keeks (i.e. 36 second video updates), search, user profiles, klusters, and more.
Expion, a Social Media Management System (SMMS) company, specializes in helping companies manage their brand images on social networks, from Facebook to Youtube to Twitter, often relying on partners' APIs to pull of some of their more interesting feats. Most recently, it was chosen by Google as a Google Plus API partner for the brand-focused Pages feature.