Uberblic is a web serice with the goal of making 3rd-party APIs and data sources interoperable, both with one another and with existing databases. The uberblic Doppelganger service connects data in many different third-party APIs by mapping an entity's 'doppelgangers', the IDs of that same entity in other APIs. Uberblic can be thought of as a dictionary for entity IDs across the web, storing a rich set of contextual data available to developers, with Uberblic’s APIs serving as a switchboard and broker between data sources.
Uberblic is another instance of what may become a trend in the world with thousands of APIs: the Meta-API. The Uberblic Doppleganger API is currently in beta, but it is quite ambitious in that it looks to position itself as a API cross-reference or mutli-plexer. Submit an ID from one API to the Doppleganger, get 4-5 IDs for matching content from other APIs.