Mozilla is now uploading new nightly builds of their mobile operating system called Firefox OS. You can download the operating system and try it out for yourself, but do so at your own risk. The nightly builds will be prone to have bugs. You can use the command line to download Gaia, which is the HTML 5 UI layer. These builds are primarily for developers to test their web apps on. Tony Chung of Mozilla has written a blog post about getting started with the new operating system.