ACM Crossroads: Operating Freely
Description of the 3 major, freely available, Unix-like operating systems: Linux, FreeBSD, NetBSD. Crossroads is the student magazine of the ACM.
COTSE-Mini UNIX Distributions
Links to 2 dozen mini Unix distributions: mostly Linux, also FreeBSD, SCO, Solaris MINIX, MINIX.
Linux and BSD, Open Source Giants
Succinct, clear, non-technical introduction to Linux and BSD, focus: how they are relevant to business.
Open Source Unix and Related Software Projects
Small page of logos and links to resources, distribution channels for the most popular, freely distributable Unix, and a few other projects. FREENIX links in English, Français, Norsk.
PIOS: Pleasant Interactive Operating System
Free Unix clone developed by PIE Software Inc., for x86 PC compatibles, to give a stable multi-user high security platform for use as a network server, programming work-horse, or desktop system; designed so even complex tasks are easy.
Thix
Unix kernel written in 1994-95; almost full implementation of POSIX.1 standard, IEEE Std 1003.1-1988. Goal: mainly to learn OS design, architecture, kernel algorithms, resource allocation, process scheduling, and memory management; free software has been compiled for it. [Open Source, GPL]