Update 18/05/2013: Added 11. Canvas Query.
2. Drawing lines in Mozilla based browsers and the Internet Explorer
Using Canviz has advantages for your web application over generating and sending bitmapped images and image maps to the browser as the server only needs to have Graphviz generate xdot text; this is faster than generating bitmapped images.
Flotr enables you to draw appealing graphs in most modern browsers with an easy to learn syntax. It comes with great features like legend support, negative value support, mouse tracking, selection support, zoom support, event hooks, CSS styling support and much more.
PlotKit is fully documented and there is a quick tutorial to get you started. PlotKit is a complete rewrite of CanvasGraph. It is better structured and supported.
With jsDraw2D, you can draw advance drawings like cubic Bezier curve, general Bezier curve. The general Bezier curve can be of any degrees including linear, quadratic and cubic, open curve passing through given points and closed curve passing through given points.
11. Canvas Query
use HTML5 Canvas like jQuery
extended canvas for gamedevelopers
easy setup for a game loop, rendering loop, mouse, touch and keyboard