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.
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.
ReVirt is part of the CoVirt project, which investigated on the use of virtual machines to provide security in an operating-system-independent manner to enable the security system to function independently from the guest operating system. ReVirt logs enough information to replay the entire intrusive sequence instruction-by-instruction so that a detailed observation on the attack can be documented. It includes a system called BackTracker that helps system administrators understand (and thereby recover from) an intrusion, by automatically identifying potential sequences of steps that occurred in an intrusion. Starting with a single detection point (e.g., a suspicious file), BackTracker identifies files and processes that could have affected that detection point and displays chains of events in a dependency graph.
GeeXboX is a standalone media player Linux distribution, similar to MoviX. It's a small bootable CD that allows you to play your favorite video (DivX, XviD, H.264, MPEG 1/2, VCD, DVD, OggMedia, Windows Media, RealMedia, etc.) and audio (MP3, Audio CD, Ogg Vorbis, FLAC, MPC, etc.) files. It also supports networking, and is able to play media from Windows/Samba share, NFS, UPnP A/V Media Servers, RTP/RTSP servers, or SHOUTcast. It supports TV-out, TV tuners, DVB cards, and WiFi cards. It is based on MPlayer, and can be used on any x86, x86_64, or PowerPC computer. It's easy to modify the source to build your own GeeXboX or use an alternative boot method.
Thinstation is a mini Linux distribution that enables you to convert standard PCs into full-featured, diskless thin clients supporting all major connectivity protocols like Windows terminal services (RDP), Citrix Ica, X, NX, telnet, ssh, etc. It can be booted from the network using Etherboot/PXE or from standard media like floppy/CD/hd/flash-disk etc. The configuration is centralized to simplify terminal management.