Code samples using HTML5 and JavaScript:
Digger
Boulderdash game written in JavaScript using the HTML5 canvas element. Use cursor keys, ESC to restart, DEL to jump to the next level.
Start here. Source here.
Netron
A graph editing library written in JavaScript using the HTML5 canvas element. Double-click to edit an element. Drag connection points to draw connections.
Start here. Source here.