Pixi.js - Fast lightweight 2D library that works across all devices
GoJS - GoJS is a JavaScript library for building interactive diagrams on HTML web pages. Build apps with flowcharts, org charts, BPMN, UML, modeling, and other visual graph types.
Snap.svg - Snap.svg is a javascript SVG library for the modern web.
mxGraph - mxGraph is a fully client side JavaScript diagramming library - jgraph/mxgraph
Raphael - Raphael.js is an Object Oriented drawing library. It is good at making in-depth diagrams with complex interactions.
jsPlumb - jsPlumb is an advanced, standards-compliant and easy to use JS library for building connectivity based applications, such as flowcharts, process flow diagrams, sequence diagrams, organisation charts, etc. More than just a diagram library.