Also, http://www.linuxdoc.org may be of interest; this is the central site for Linux HOWTO's, FAQs and guides. But you probably already knew this one, right? ;-)
If you would like to get these pages in some other format, go to http://people.debian.org/~wouter/, where you'll find links to HTML, PDF, DVI and LATEX-files of this thing.
Corrections and suggestions are accepted at
mailto:wouter@debian.org.