Most of these games are open source and some have a page with more information about their implementation.

The game includes simple box2d based car physics, multiplayer, waypoint based racing AI, zoomable camera that follows an object in the game world, etc.
Source code: https://github.com/domasx2/banditracer-client and more Infos: http://banditracer.eu/about

Classic space shoot'em'up. Source code on github
The goal is to destroy all circles with your squares. More info and source code on the Evil Circles page.

Blog post about this easter egg in the Nokia Maps application.
Shoot em up. More info about the simple animation framework used in this game and the source code.
Conway's Game of Life in JavaScript (see Wikipedia on Game of Life).
More info and source on github
Physics game. Integrates Box2d. More info and source code on the Planetary page.
CPU heavy landscape generator. Ground features are derived from perlin noise and drawn as ISO landscape.
More info and source on github
A simple real-time strategy game based on the board-game Pandemic. Source code: https://github.com/oberhamsi/y8y2
Ludum Dare 48h hours entry The Last Adventurer. This is a game about losing your companions. It's an action RPG with the twist being that you start with a party of five and lose one member at a time until the final quest when you're alone.

Halloween Pumpkin Juggling (available on Chrome Webstore).
Remake of Utopia (1981). One of the first real time strategy games.
Audio, violence, music experiment. Only works in Firefox3+.
More info and source on github

A multiplayer online panda simulation. Works best on Google Chrome 13, Safari 5, or the iPad (iOS 4). Tested also with Firefox 6. More info and source code.
Mouse event example draw sparkles.
Sprite performance test. The smoother the sprites move, the stronger your PC.
Shoot em up.
the same code in both languages
A very minimal GameJs app: A pulsating circle that reacts to clicks. Interesting because it shows how a very simple demo can be structured in GameJs. The source is about 70 LOC.
audio, explosion sketch
:(
Tech demo for an RPG. Skills, Line of Sight, Melee, Ranged, Item Managment, Pathfinding,...

On hold. Political strategy game. Round based, casual.

Networking with websockets (on hold). The two green soldiers are controlled by me & my buddy.