I just released the first version of
CopperLicht, a new 3D engine implemented completely in JavaScript. It runs entirely in the browser and uses WebGL. (WebGL is a new 3d drawing API which is supposed to be supported in the next generation of web browsers.) Doesn't sound too awesome maybe, but look what CopperLicht can do:

Basically, it is pretty fast and can render huge maps like here a full quake 3 level in playable speeds. (If you notice, this one is the quake map from the Irrlicht SDK). You can try out the
demo yourself here.
CopperLicht is free to use. You can use
CopperCube as world editor, so you can edit your worlds in 3d and write your game with CopperLicht. The API of CopperLicht is pretty easy to understand, and if you ever tried out Irrlicht, you'll notice that those are very similar. The SceneGraph and Material API is nearly the same, and loading textures and extending the engine works very similar as in Irrlicht.
CopperCube has been released in a new version as well now, it now also supports publishing its 3D scenes as WebGL, using CopperLicht of course.
This is the first release of CopperLicht, and it's an alpha version, so if you have any suggestions, comments, feature requests and similar, please don't hesitate. :)