A lot of different tools were mentioned in this book. Here are links to where the source code for these tools can be found on the Internet.
Linux kernel
http://www.kernel.org and ftp://ftp.kernel.org contain all of the different versions of the Linux kernel source code. http://www.kernel.org/git/ contains a listing of all git trees in use by the different kernel developers.
gcc
http://gcc.gnu.org/ is the main site for everything related to the GNU C Compiler.
binutils
http://www.gnu.org/software/binutils/ is the main site for all information about binutils.
make
http://www.gnu.org/software/make/ is the main site for all information about make.
util-linux
http://www.kernel.org/pub/linux/utils/util-linux/ is the directory where all versions of util-linux can be downloaded.
module-init-tools
http://www.kernel.org/pub/linux/utils/kernel/module-init-tools/ is the directory where all versions of module-init-tools can be downloaded.
e2fsprogs
http://e2fsprogs.sourceforge.net/ is the main project page for the e2fsprogs package.
jfsutils
http://jfs.sourceforge.net/ is the main project page for the jfsutils package.
reiserfsprogs
http://www.namesys.com/download.html is the main project page for the reiserfsprogs package.
xfsprogs
http://oss.sgi.com/projects/xfs/ is the main project page for the xfsprogs package.
quota-tools
http://sourceforge.net/projects/linuxquota/ is the main project page for the quota-tools package.
nfs-utils
http://nfs.sf.net/ is the main project page for the nfs-utils package.
udev
http://www.kernel.org/pub/linux/utils/kernel/hotplug/udev.html is the directory where all versions of udev can be downloaded.
procfs
http://procps.sourceforge.net/ is the main project page for the procfs package.
patchutils
http://cyberelk.net/tim/patchutils is the location for all of the patchutils releases.
git
http://git.or.cz/ is the main site for the git project.
ketchup
http://www.selenic.com/ketchup/ is the main project page for the ketchup program.
quilt
http://savannah.nongnu.org/projects/quilt is the main project page for the quilt program.
distcc
http://distcc.samba.org/ is the main project page for the distcc program.
ccache
http://ccache.samba.org/ is the main project page for the ccache program.