btfs can be used as /init for constructing a run-time environment before running the real init. It supports extracting compressed (*.cgz, *.cbz2) and uncompressed (*.co) cpios located on a compile-defined directory (/). Also, it creates a tmpfs filesystem as the new root, if / isn't one already and the purpose of the initramfs isn't for starting a system in another location (disk, network, etc.). That will allow for the data on / to be swapped to disk when swap devices are activated later.
LILO is a Boot loader for Linux/x86 and other PC operating systems. It is responsible for loading your Linux kernel from either a floppy or a hard drive and passing control to it. It is capable of booting beyond cylinder 1024 of a hard disk if the BIOS supports EDD packet call extensions to the int 0x13 interface. LILO can also be used to boot many other operating systems, including DOS, Windows (all versions), OS/2, and the BSD variants. The LILO distribution includes full source, documentation and support files.
PXE Knife is a tool for booting various floppy based utilities via syslinux, allowing them to be booted off a CD, a hard drive, or over the network via PXE. PXE Knife can be used with a number of commonly used tools such as hard drive manufacturer's utilities, memory testers, Linux recovery disks, Windows password changers, pre-configured PXE Knoppix booters (just add DVD), and a number of other utilities. It takes advantage of syslinux's menu system, so it's easy to navigate.
Debian From Scratch is really two related components in one. First, it's a live bootable CD image that is designed to provide a full-featured kernel and rescue environment. It includes filesystem tools, editors, C compilers, Python, Perl, and everything you need to manually install Debian on a new machine. On ix86 machines, Grub is used to boot directly from the CD. There is also a program that is used to create the DFS CD images. It is highly configurable and can be used to create other custom bootable CD or DVD images. You can include whatever kernel or packages you want.