GNU/Linux is all about choice. Other distributions of GNU/Linux have their devotees, and each in its own way contributes significantly to the overall development of GNU/Linux. Other distibutions include Red Hat, Mandrake, SuSe, and Slackware. There are many distributions indexed at http://www.linux.org/dist/index.html. An early distribution, still being maintained is Slackware available from http://www.slackware.com/. Clearly, Red Hat, available from http://www.redhat.com/, is an excellent distribution responsible for gaining a lot of exposure for GNU/Linux.
While we use Debian GNU/Linux in this book as the underlying distribution what we say here applies to most distributions most of the time.