SystemRescueCd is a Linux system available from a bootable CDROM that provides an easy way to perform administrative tasks on your computer, such as creating and editing the partitions of the hard disk or backing up data. It contains a lot of system utilities (such as parted, partimage, and fstools), and basic programs (such as editors, midnight commander, and network tools). It also includes GParted, a Partition Magic clone that makes editing partitions easy with its graphical user interface. This CDROM aims to be very easy to use and accessible to everybody, and it also provides advanced personalization features.
INSERT (the Inside Security Rescue Toolkit) aims to be a multi-functional, multi-purpose disaster recovery and network analysis system. It boots from a credit card-sized CD-ROM and is basically a stripped-down version of Knoppix. It features good hardware detection, fluxbox, emelfm, links-hacked, ssh, tcpdump, nmap, chntpwd, and much more. It provides full read-write support for NTFS partitions (using ntfs-3g), and the ClamAV virus scanner (including a fairly recent signature database and a GUI). It provides partition handling with gParted and also has a network boot facility.
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.
iloog is a Gentoo-based live CD targeted mainly at students and scientists. It features UnionFS filesystem support that enables you to write everywhere on the LiveCD and install extra packages, a graphical X environment through the Fluxbox window manager, many programming editors and IDEs, and a plethora of scientific applications, including Octave, Namd, Merlin, and full (La)TeX support.
Portable Linux is a tool that lets you create bootable USB and removable drives using popular Live CDs based on Casper (like the Ubuntu family of distributions). It sports some unique features. The live setups it creates let you use the remaining disk space on your USB drive to store and transport files between computers, as usual. If your distribution supports persistence, the files and settings you edit on your live Linux distribution are persisted across reboots. Finally, you can access the area used to store your files from within your Linux distribution.