ThreeJS - http://threejs.org/
Helps you create webgl applications easily. Had some issues with parts of the library/platform not working with other parts due to version conflicts. At the time of this writing the the JSON exporter for Blender did not work with bone based animations.
A file format and exporter which can be used with ThreeJS. Supports bone animations.
Pixi - http://www.pixijs.com/
A 2D renderer which uses WebGL but fallsback to Canvas. A fantastic library but is a bit bulky. Noticed some inconsistencies between Graphics (vector style) rendering in WebGL rendering and 2D canvas rendering. Filters are not compatible when Canvas fallback is used.
A library which helps you add Sounds to websites.
CLMTrackr - https://github.com/auduno/clmtrackr
Facial feature recognition and tracking. Works better with video/webcam than still images. By default uses WebGL but can fallback to a slower less precise mode using Canvas 2D.
jsfeat - http://inspirit.github.io/jsfeat/
Computer vision.