Second the vote for Mixamo... awesome service, makes creating animation loops really fun and easy.

We're reworking the animation system in Three.js, so soon you'll be able to make your animations in Mixamo, and deliver them on the web. You can do it yourself with Three.js, or with our help using http://studio.verold.com (though, if you're going to do another Gangnam style, please use a better remix - like https://soundcloud.com/stirling-inch/pretty-gangnam-fly-stir...)