Cfengine is a tool for setting up and maintaining BSD and System-5-like operating system optionally attached to a TCP/IP network. You can think of cfengine as a very high level language, much higher level than Perl or shell: a single statement can result in many hundreds of operations being performed on multiple hosts. Cfengine is good at performing a lot of common system administration tasks, and allows you to build on its strengths with your own scripts.
SFI Director is a tool for managing distributed, heterogeneous UNIX Systems. Its functionality includes System Configuration, Application Distribution, NIS and NIS+ Management, User Creation, and Dynamic System Documentation. It is in service at a number of sites, managing networks of 50 to 200+ UNIX nodes, under Linux, Solaris, Digital UNIX, and HP-UX.
Pocket Linux is an almost minimal, one floppy linux system designed to quickly convert PC workstation into secure linux-based workstation using ssh to connect to remote host (other networking clients are also supported). It supports bootp for determining host IP and other network parameters (there's also manual configuration possible, but bootp is recommended). In addition to workstations equipped with a network card (ethernet or arcnet), you can also use Pocket Linux on a PC equipped with a modem. Modem is automatically detected and then PPP connection is made.
Screen is a full-screen window manager that multiplexes a physical terminal between several processes, typically interactive shells. Each virtual terminal provides the functions of the DEC VT100 terminal and, in addition, several control functions from the ANSI X3.64 (ISO 6429) and ISO 2022 standards (e.g., insert/delete line and support for multiple character sets).
John the Ripper is a fast password cracker, currently available for many flavors of Unix, Windows, DOS, BeOS, and OpenVMS. Its primary purpose is to detect weak Unix passwords. It supports several crypt(3) password hash types commonly found on Unix systems, as well as Windows LM hashes. On top of this, lots of other hashes and ciphers are added in the community-enhanced version (-jumbo), and some are added in John the Ripper Pro.