Oleg Romashin, a Nokia engineer, has been working on porting Firefox OS (previously known as Boot 2 Gecko) to the Raspberry Pi, and has uploaded a YouTube video showing a Firefox OS running on the device, including a WebGL teapot demo running at 60 fps. This Firefox OS build is based on Debian Squeezy, with plain EGL rendering, no Widget Toolkit backends and no X11. Some parts do not look very smooth yet, but this demo looks promising.
If you want to try it yourself, you can download the WebGL teapot build. Mozilla patches with LinuxGL widget backend are also available at http://hg.mozilla.org/users/romaxa_gmail.com/embedipc_queue/file/linuxglpure. If you have the N9 smartphone or Beagleboard, it looks like you can also try this. Check files in http://romaxa.info/b2g/.