Breakouts. Breakouts is a really cool initiative started by Matt Greer to create a single game using multiple engines. Matt (along with several other contributing developers) has created Breakout using several different HTML5 engines. As of this post, Crafty, CreateJS, FriGame, Frozen, ImpactJS, LimeJS, MelonJS, Platypus, and Quintus all have working implementations of Breakout on the site. Oh, is Platypus bold? Whoops, I'll fix that later.
If you want to check out the code involved, the development style, and features across several HTML5 engines, Breakouts is a fantastic starting point. Also, be sure to check out the convenient feature comparison table.