Linux4Geeks is a LFS-based small distro which works around several problems and issues mainstream Linux distributions have. It offers different versions compiled for each architecture and has all the packages required for a slim installation including a firewall and network administration tools, amongst others.
alcolix is a minimal Linux rescue distribution with the goals of being small, compatible, and very usable. It has a cozy shell and a multitude of partition rescue/editing tools, all based on up-to-date releases (e.g., 2.4.x kernel with USB support). It uses cpio.bz2 data disks and has a full GRUB bootloader, memtest86, and more.
Salvare (from the Latin "to rescue") is a small Linux distribution designed for small, credit-card sized CDs which typically hold around 34MB. More Linux than tomsrtbt but less than Knoppix, it aims to provide a useful workstation as well as a rescue disk. In addition to providing a rescue environment similart to tomsrtbt, it adds OpenSSH, a graphical and text mode Web browser (Links), security tools such as chkrootkit, nmap, and tcpdump, the ability to apt-get install additional software from Debian into tmpfs, the ability to run entirely from RAM, and much more. It's also customizable using a simple source-code based package management system.
stresslinux is a minimal Linux distribution that runs from a bootable CDROM or via PXE. It makes use of some utitlities such as stress, cpuburn, hddtemp, lm_sensors, etc. It is dedicated to users who want to test their system(s) entirely on high load and monitor the health of these systems.
ThePacketMaster Linux Security Server is a CD-based security auditing tool that boots and runs penetration testing and forensic analysis tools. It is handy for security auditors. Some tools included are nessus, ethereal, The Coroner's Toolkit, chntpw, and minicom. It includes modules for any Linux 2.4.20 SCSI driver.
BG-Rescue Linux is a Busybox and uClibc-based rescue system with a 2.4 series Linux kernel. It supports full read/write support for NTFS using ntfs-3g. It is loaded from two floppy disks, a bootable CD-Rom, or a USB Stick. The system runs entirely in RAM. It supports a wide range of hardware (including SATA and DM/LVM2) and filesystems (including ext2/3, hfs/hfs+, and xfs) and can serve as a full backup/restore system for MS Windows systems which use FAT12/16/32 or NTFS. It also includes many utilities, including strong compresstion tools like lrzip. Automatic loading of the antivirus-program F-Prot from cdrom or usbstick is supported.
Thinux is a thin-client server on a live CD. It boots a network of diskless computers to automatically start an application such as a Web browser. Each thin client machine acts as a cluster node to share its processing and memory resources with each other to take the load off the server. It is a turnkey solution that does not change nor rely on your existing systems to run. By booting from a removable CD, it does not lock-in the user so it is convenient to test. It is ideal for any organizations that require large deployment of software automatically and cost effectively.