HTML5 is the new standard for World Wide Web content, which is currently under development. This new web technology comes with several cool and promising features for your browser like video/ audio playback, drag-and-drop, etc without the need of any external plug-ins.
Though several features are still in their early stages, you can try some of those cool features in your latest browsers. HTML5 gaming is one of them that you can play without flash plug-in.
HTML5 Games is an online gaming repository that gives you insight into the world of HTML5 games. There are many genres like arcade, puzzle, sports and much more to play for free.[via]