There are quite a few scripts/tools out there that will help
in automatically generating a toolchain, a root filesystem,
a ROM image, and other components of an embedded Linux system.
This is a collection of such tools, scripts, tipps and tricks:
- buildroot: http://www.uclibc.org/cgi-bin/cvsweb/buildroot/
This is a set of scripts maintained by Erik Andersen (uClibc,
BusyBox?, TinyLogin?, etc.) that can be used to build quite a
few components (including toolchain for host and target
binaries.) Though I haven't used buildroot, the content of
the scripts is one of the best I've seen (well organized
and thorough).
- PTXdist: http://www.pengutronix.de/software/ptxdist_en.html
This tool is maintained by Robert Schwebel (utelnetd, RTAI
documentation, etc.) that creates root filesystems. It
relies on the use of a KConfig-based frontend. There are
nice screenshots.
- Bill Gatliff's build script:
http://billgatliff.com/twiki/bin/view/Crossgcc/BuildToolchainScript
This is one script which builds a toolchain made by Bill
Gatliff (gdb stubs, regular contributor to Embedded Systems
Programing, reviewed my book, etc.)
- Craig Hollabaugh's build scripts:
http://www.embeddedlinuxinterfacing.com/sourcecode.shtml
These are the scripts Craig used in his "Embedded Linux"
book. There is a buildtoolchain.tar.gz, which is the set
of script used to build the toolchain, and there's
buildrootfilesystem, which is used to ... well, build
the root filesystem 
- Richard Atterer's build script:
http://home.in.tum.de/~atterer/debian/
Again, a script to build a toolchain.
- David A. Desrosiers' build script:
http://libarynth.f0.am/cgi-bin/view/Libarynth/CrossCompiler
Yet another toolchain build script.
- "Peewee Linux":
http://www.peeweelinux.com
"an environment that makes the configuration and installation of a Linux operating system on an embedded platform as easy and painless as possible"
- http://www.bluewaternz.com/startoff/armlinux.htm
[For ARM targets] a script which conveniently builds binutils, cross compiler, glibc, and the kernel.
[From: Karim Yaghmour et. al. on the etux mailing list.]
