Linux From Scratch: http://www.linuxfromscratch.org/

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.
    Hints :: The Hints project is a collection of documents that explain how to enhance your LFS system in ways that are not included in the LFS or BLFS books.
    LiveCD :: The LiveCD project provides a CD that is useful as an LFS build host or as a general rescue CD.
    Patches :: The Patches project serves as a central repository for all patches useful to an LFS user.