Games programmers here might be interested in this project I have been working on the past few weeks. Have a look here:
The maturity and robustness is commendable, and Emscripten has become a viable alternative to Flash and Native Client. I develop a graphics system called gfxapi, which targets both Emscripten and PNaCl targets. With GLES2 and EGL support, developing 3D graphics against Emscripten is very similar to developing 3D gaphics for Android. Also recently, Unreal Engine 3 was ported over to the web, which goes to show that Mozilla's approach has the capability to scale as well.
The technical details of the ScummVM port can be discussed at the Emscripten mailing list.