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.

Textor

A text editor library with JavaScript, HTML and CSS syntax highlighting using HTML5 canvas.

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.