Vega & Vega-Lite
Visualization Grammars

Vega is a declarative format for creating, saving, and sharing visualization designs. With Vega, visualizations are described in JSON, and generate interactive views using either HTML5 Canvas or SVG.
Toolkits
Vega is a visualization grammar, a declarative language for creating, saving, and sharing interactive visualization designs. With Vega, you can describe the visual appearance and interactive behavior of a visualization in a JSON format, and generate web-based views using Canvas or SVG.
Vega-Lite is a high-level visualization grammar. It provides a concise JSON syntax for supporting rapid generation of visualizations to support analysis. Vega-Lite support interactive multi-view graphics. Specifications can be compiled to Vega.
Systems
Lyra is an interactive environment that enables custom visualization design. Without writing any code, designers can create visualizations on-par with hand-coded D3 and Processing.
Voyager is a visualization interface for data exploration. It provides an interface for specifying Vega-Lite specification, with chart recommendation powered by the Compass visualization recommender engine.
Compassql is a visualization recommendation engine. Given user query, it suggests visualizations, ranked by both data properties and perceptual principles.
Utilities

Datalib is a JavaScript data utility library. It provides facilities for data loading, type inference, common statistics, and string templates. This is a standalone library useful for data-driven JavaScript applications on both the both the client (web browser) and server (e.g., node.js).

Vega's 3rd Party Integration

The MediaWiki Graph extension allows you to embed Vega visualizations on MediaWiki sites, including Wikipedia.