Koala is a Ruby library for Facebook that allows developers to access the Facebook Graph API, REST API, OAuth validation, realtime updates, and test users. It supports JRuby, Rubinius, and REE in addition to multiple versions of vanilla Ruby.
According to a post from a Google engineer, intended to be private to the search giant's employees, the Google+ API was not ready at launch. Google's Steve Yegge also badmouthed the read-only, public API. When the company's new service was only two weeks old, I wondered whether the Google+ API was intentionally late. Maybe it was just truly late.
Online diagramming service Creately opened its Creately API to the public this month, and with some surprisingly innovative features. While providing obvious features to make its service available to outside developers, and several "above and beyond" features, such as easy embedding of diagrams, Creately has done something fairly unique: open up its own, web-based file format for other developers to use.