Recently on #gentoo we saw a few questions about Gentoo Live USB, which we thought was an awesome idea. Turns out that many people were looking for this but few were finding it. We'd build an Ubuntu Live USB stick before and have been using Gentoo for years, this shouldn't be too hard... We cloned the ISO image for the Live CD, similar steps as we used on Ubuntu Live USB. Ran the extlinux and used the files from the isolinux folder in the Gentoo ISO. Booted off the disc on our test laptop and boom! Gentoo Live USB!