Southern writes:  

Linux From Scratch (LFS) is a project that provides you with step-by-step instructions for building your own custom Linux system, entirely from source code.

Currently, the Linux From Scratch organization consists of the following subprojects:

LFS :: Linux From Scratch is the main book, the base from which all other projects are derived.
BLFS :: Beyond Linux From Scratch helps you extend your finished LFS installation into a more customized and usable system.
ALFS :: Automated Linux From Scratch provides tools for automating and managing LFS and BLFS builds.
CLFS :: Cross Linux From Scratch provides the means to cross-compile an LFS system on many types of systems.
HLFS :: Hardened Linux From Scratch focuses on building an LFS system with heightened security.

more: Linux From Scratch!