GraphJSON is a generalized JSON representation of Graphs that can be used for Graph Data model documentation and to represent “Graphy” data. You can read more about the GraphJSON format here.
The GraphJSON and GraphJSON.io were heavily inspired by GeoJSON and GeoJSON.iorespectively.
GraphJSON.io is current in experimental Alpha. In early next year you can expect an interactive code mirror to generate GraphJSON on the fly. The project is currently being ported to angular -- the original code base is here and was pulled together by Mark Millman, Huston Hedinger of GraphAlchemist and deployed by Matt Robenolt. A big thank you to Alistair Jones who is responsible for the geometry and layout of the Graph with his original arrows project and whose original (unlicensed) code powers the current site.