AROS : Free, lightweight, efficient and flexible desktop operating system. Amiga Research Operating System, aiming at being compatible with AmigaOS at the API level.
GeeXboX : Linux based media center operating system.
Gobo Linux : Linux based operating system. It's file system is the database. Each program resides in its own directory.
Haiku OS :Open source operating system that specifically targets personal computing. Inspired by the BeOS.
Inferno : Compact operating system designed for building distributed and networked systems on a wide variety of devices and platforms.
Kolibri OS : Small and ManuetOS based operating system.
MenuetOS : Written entirely in 32/64 bit assembly language. Menuet supports 32/64 bit x86 assembly programming for smaller, faster and less resource hungry applications.
MINIX : Unix-Like operating system. Created for educational purposes. MINIX also inspired the creation of the Linux kernel.
OpenBSD : Security and stability of an operating system that is too high.
Oracle Solaris : Operating system based on Solaris created by Sun Microsystems, now a part of Oracle Corporation.
OSWA Assistant : Free, self-contained, wireless-auditing toolkit for both IT-security professionals and End-users alike.
ReactOS : Windows-like, fast, small and free operating system.
Slammp : Linux based live cd for Home Server.
Webian : Web browser based cloud operating system by Mozilla.