Graphics library (low level)
- Raphael - http://raphaeljs.com/
- D3.js - http://d3js.org/
- Arbor (a graph viz lib) - http://arborjs.org/
Diagram Library
- JointJS - http://www.jointjs.com/
- jsPlumb - http://jsplumbtoolkit.com/jquery/demo.html
Misc Resources