virtfs a nice automatic tool for configuring virtual services based on Perl script
Linux Public Access HOWTOan old and not updated for 5 years document describing Linux-based ISP, some nice hints on equipment (serial boards) and performance
Resources, not related to the topic of the document ;-)
I also maintain a list of computer/network security related books with (where available) reviews and online availability. It is posted at http://www.chuvakin.org/books. If you have a book that I don't list please use the form on the page and I will add it to the list and maybe review it later.