Tin Hat is a Linux distribution derived from hardened Gentoo. It aims to provide a very secure, stable, and fast desktop environment that lives purely in RAM. Tin Hat boots from CD, or optionally USB pen drive, but it is not a LiveCD in that it does not mount any file system from the boot device. Rather, Tin Hat employs a massive squashfs image which expands into tmpfs upon booting. This makes for long boot times, but remarkable speeds during human-computer interaction.
BG-Tiny Linux Bootdisk is a Linux bootdisk that does not use a ramdisk, so it will run on computers with very little RAM. It is basically a somewhat extended fork of Tiny Linux Bootdisk. It is based on Linux 2.4 series, uClibc, and BusyBox. It includes dosfsprogs, e2fsprogs, gpart, lilo, and ms-sys. Supported filesystems are ext2, ext3, iso9660, tmpfs, and vfat.
Kevux is an operating system based mainly on GNU operating programs and a Linux kernel, all compiled with uclibc instead of the more common glibc. It is not FHS or LSB compatible. Compared to other Linux distributions, Kevux is space efficient (making it suitable for USB disk operation) and difficult to hack into.