I recently wrote a tutorial for getting started with the Crafty HTML5 game engine. Crafty makes it easy to create 2D games in HTML5. It's especially awesome for prototyping and game jamming.
In my tutorial, I walk you through the process of creating a simple top-down adventure game from soup to nuts. By the end of it, you'll have a working game you can build upon or use to help you make more games with Crafty.You can go through my tutorial here on Build New Games.