Finnix is a small, self-contained, bootable Linux CD distribution ("LiveCD") for system administrators, based on Debian testing. You can use it to mount and manipulate hard drives and partitions, monitor networks, rebuild boot records, install other operating systems, and much more.
Powertweak-Linux is a tool to tune your system to its optimal performance settings. It started life as the replacement for the now obsolete kernel option 'tune PCI bridges', and has been extended to provide more features and support more chipsets. It can also tune network/filesystem performance using /proc/sys entries, disk elevator settings, and x86 CPU registers (needs 2.2.18 or 2.4.0test kernel), CDROM speeds, hdparm type features, and Sony VAIO backlight. It has both a GTK GUI and a text-based lister.
Ivman is a flexible userspace volume manager for Linux. Originally an automounter, it can also be used to run arbitrary commands when certain devices are added to or removed from the system, when properties on existing devices change, or when devices emit conditions. Unlike gnome-volume-manager, it runs from a console. It uses D-BUS and HAL to listen for new devices, and uses pmount for mounting.
YanC (Yet another nV Configurator) is a small tool which you can use to change the nVidia and ATI-specific settings (almost) as easily as with the Windows drivers. You can edit the settings for AGP support, the Cursor Shadow, the nVidia logo, Digital Vibrance Control, and, of course, TwinView for the nVidia drivers. For the ATI drivers, it offers support for the overlay settings, anti-aliasing, and dual monitor configuration.
SimMon is a cross platform monitoring tool which runs on almost any OS that supports the Java Virtual Machine 1.4+. Monitoring is done through the execution of existing monitoring scripts (Perl/VBS) or existing shell commands. Currently monitoring scripts are available for Solaris, Linux, Mac OS X, and Windows based systems. Network devices can be monitored via the integrated SNMPv1 scheduler.