Boot to Gecko can be loaded up on either the GSM Galaxy Nexus or the Verizon Galaxy Nexus (not the Sprint Galaxy Nexus for some reason though.) A number of things are working in the build, including touchscreen input, ADB, WiFi, the lockscreen, the homescreen, and Firefox. Unfortunately, there are no soft keys, so navigation can be trouble, and in addition, screenshots, the camera, and cell service are listed under partially/not working.
Still, it could be a fun experiment if you want to give it a shot. The ROM has to be installed via fastboot, but if you're comfortable with that, you can get what you need at the sources.