Zencoder
Zencoder is the creator of an open-source HTML5 video player, Video.js, built with Javascript, HTML, and CSS. Video.js plays video via native playback in all HTML5 browsers and devices, or through Adobe Flash when HTML5 playback is not available.
Blobby Volley
Since 2016 there is also a version of Blobby Volley 2 available for browsers which utilizes HTML5 for rendering.