[teamonkey]

Akihabara is probably the most complete JS game lib, but man is it messy. It has clearly grown organically and is in need of a good refactoring.

CakeJS is a bit cleaner, it has a nice scene graph, but it's at a much lower level than Aki. There's none of the useful game basics like collision detection so you have to write those yourself. http://glimr.rubyforge.org/cake/canvas.html

Raphael is similar to Cake in scope but for SVG/VML instead of Canvas. http://raphaeljs.com/

Finally there's Processing.js, which is the javscript port of the Java library. http://processingjs.org/