Leetnux is a Linux distribution specifically designed for Linux users who want maximum configuratibility. Therefore, the installation is quite hard and absolutely nothing is done "automagically" as in modern Linux distributions, but the user has total control over installation and configuration.
Mandriva is an RPM-based Linux distribtion. It excels at usability and simplicity, features thoroughly preconfigured KDE and GNOME desktops, and includes cool tools like supermount (transparent access to removable media) and DiskDrake (a full-featured graphical hard-drive partitioner). Unlike former versions, Mandriva is not a tuned-up Red Hat, but a very mature Linux distribution on its own. Mandriva is published by a company, but is a completely open and transparent free-software project.
MINIX is a free UNIX clone that is available with all the source code. Due to its small size, microkernel-based design, and ample documentation, it is well suited to people who want to run a UNIX-like system on their personal computer and learn about how such systems work inside. It is possible for a person unfamiliar with operating system internals to understand nearly the entire system after just a few months use and study.
muLinux is a minimalistic, but mostly complete, script-based Linux distribution that fits on a single 1722k floppy. X11, GCC, VNC, and TCL addons are supported on additional floppies. It includes many basic system functions, such as PPP and Ethernet support, mail processing, NFS, Samba, FTP, IRC Finger, ipfw, etc.
Open Distributed Data Acquisition System Linux is a mini distribution of GNU/Linux intended for use on the ODDAS project. It contains a shell and some basic commands plus servers for HTTP, FTP and telnet. It also includes the capability to perform syslog over the network, and contains a very simple mail program which allows alerts to be forwarded across the network. The whole thing squeezes into about 3M of flash on an Intel [3-6]86 processor.
The OpenBSD project produces a free, multi-platform 4.4BSD-based UNIX-like operating system. Its goals emphasize portability, standardization, correctness, proactive security, and integrated cryptography. OpenBSD supports binary emulation of most programs from SVR4 (Solaris), FreeBSD, Linux, BSD/OS, SunOS, and HP-UX.
Pklinux-bigi is a Slackware derived distribution based on glibc 2.2 and Linux 2.4.0-test11. It can run on 386, 486, 586, and Pentium machines with only 4 MB of RAM. Builtin features include IP tunneling, firewalling, encapsulation, QOS(based on ipv4 RSVP), kernel debugging, loopback, network block device, and numerous filesystems (including ntfs and sysV). It contains Apache, proftpd, bind 9.0, syslogd, sendmail, iptables, iproute2, and gated. NAT configuration by iptables is included by default. It is a loopdisk based distribution which can be directly run from DOS, no hdd partitioning needed. This distribution is kept as minimal as possible and it can be useful in places where you want a low end computer to act as a firewall, webserver, mail server, router, or an alternative to zipslack.