Google Chrome Frame, Enable open web technologies in Internet Explorer.

General Purpose
jquery
mootools
Modernizr
prototypejs

HTML Canvas
processingjs
easeljs
gury
MooTools Canvas Library
pixastic

3D
three.js
C3DL
copperlicht
j3d

Animation on Canvas
cakejs

Vector drawing on Canvas
Paper.js
Raphaël

Charts
rgraph

Javascript Graphics library
JSGL
unveil : Data driven application framework

Media
popcornjs
jsfx

Game
craftyjs
gameQuery
xc.js
mibbu
LimeJS
Cocos2D
akihabara
FlixelJS
GameJs
Gamma

Mathematics
Sylvester

Tutorials, examples and references :
creativejs
diveintohtml5
Chrome Experiments
html5games
HTML5 based Game Engines
Js Game Engines