SkyOS
Open-source, full featured graphical (GUI) 32-bit operating system for x86 386+ architecture; network and Sound Blaster support, mice, video, and many file systems. Website shows requirements, screenshots, status, downloads, documentation, contacts, members, forum, mail list. You Would also find info related to operating system, world, software, internet, tools, utility, download, free, files, skyos, linux, microsoft, windows and much more.

BoxOS
Connects many open source projects together in one neat package; kernel, boot loader, graphical user interface, console user interface, applications, programming languages, drivers, file system support for BeOS, Linux, Windows 95/98/NT. [Open Source, GNU]

Degenerate OS
Fits in boot sector, minimal debug-like interface from which you can do much with much effort, few commands, all values in hexadecimal, case and white space sensitive. One all-text page with description, assembly listing. [Open Source, GPL]

Domainatrix
Assembly language OS for Intel/AMD x86 architecture made specifically for serving the Web, written originally for the programmer's personal interest and education after moving to the PC platform from his old 8-bit machine. Philosophically similar to V2 OS. You Would also find info related to OS, Assembly Language, machine code, x86, Networks, TCP/IP, IPv6, Operating Systems, IA-64, Itanium, Servers, Webservers, Intel and much more.

Download Operating System: LSD
By LadSoft; developed years ago and improved since then; planed for redesign to make a viable OS; updates soon. Extant version is good sample of programming standard PC hardware (no PCI) and managing x86 pmode resources. [Copyrighted Freeware]

FlashOS
Simple OS for x86 CPUs. First designed by Kenneth Garin who still directs and designs project and allows help by others to develop it into a working system. Goal: create whole OS like DOS, with our own ideas of how OS should work: not another clone. [Open Source, GPL]

Hactar
Claims: all new, no equivalent design in extant OSs, an adventure into something really different, an answer to a What if? Runs on 386+, system disk is floppy, kernel size 32Kb; manages 4Gb RAM, 2Gb disk; semi-multitasking; unusual interface. [Open Source, WTOF PL]

HanoiOS
Self booting x86 OS implementation of Towers of Hanoi puzzle, very simple bootstrap loader and kernel; boots, presents shell-like prompt for valid integer input, used by kernel as count of disks to solve, prints list of moves. You Would also find info related to Amit, Singh, Amit Singh, Art, Computer Art, Drawing, Painting, Sketching, Oil Painting, Crayons, Pastels, Pencil Colors, Audi, TT, Roadster, Quattro, Empeg, Rio, RioCar, MP3, IrDA, Debian, ARM, Embedded, Fitness, Hanoi, Hanoimania, Sega, Dreamcast, Sega and much more.

Plex86.org
Was FreeMWare. Extensible PC virtualization program to allow running multiple OSs at once on one processor. Runs as much OS and application software natively as possible, the rest emulated by PC virtualization monitor. [Open Source, LGPL] You Would also find info related to plex86, x86 virtual machine, virtualization, virtualisation, emulation, emulator, linux, bochs and much more.

PM_SZ_OS
Protected mode, 32-bit OS for i486 CPUs and up, full network stack, supports several filesystems, paging, deferred procedure call support, and virtual multiple screens with different resolution and scrollback. Free download.

RDOS
Multi-process/threaded protected mode OS for all i386+ systems, written in all 16-/32-bit Assembly in TASM, fully PROMable so can port to embedded systems with no keyboard and/or screen, stable and secure via segment protection and paging. [Open Source, GPL]

ReWin
Rewriting Windows: new OS now being designed for computers with Intel (or compatible) i386, i.e., with multitasking functions built into the processor. Will be Windows compatible, but won't be a Windows clone: will give Windows executables the needed API so they can run correctly. English/Italiano.

ScottsNewOS
Runs on i386+ compatible, working GUI even on 4 MB. Coded in Assembly, C. Brief description, download link. [Open Source, GPL]

ShellOS
Development of a 32-bit, monolithic kernal with preemptive, prioritized multitasking. You Would also find info related to 286, 32 bit, 32-bit, 386, 486, 586, 80286, 80386, 80486, 80586, 80x86, a20, AMD, bit, byte, cooperative, CPU, FAT, FAT12, FAT16, FAT32, filesystem, free, freeware, GPL, graphical, graphical user interface, GUI, GUI-based, IBM, Intel, kernel, keyboard, mF and much more.

SuperDOS
Multitasking, multiuser business OS; small (100K), integrated file system, low maintenance. Main purpose: fast business online transaction processing. Usually used in vertical markets such as transportation. Not a (unrelated to) DOS variant. By Bluebird Systems.

Synapse Operating Services
Protected mode, multitasking support, 32-bit; developed on x86-32, intended to run on x86-64 with some changes; DOS-like, but not fully compatible, use: to run ported DOS programs up to 512K. At SourceForge. [Open Source, BSD]

TABOS
Merger of TAB-DOS Alphasystem rewrite of PTS-DOS source code, and AladinOS; and a distant relative of FloppyOS and MenuetOS. Goal: tiny, fast, written in pure x86 Assembly. [Open Source]

The Mobius
OS for IA32 processors (i486 and up, and compatible), 32-bit graphical monolithic kernel, modular device drivers and GUI. Supports GCC (Cygwin), Visual C++, Unicode throughout; plans for many GNU tools are underway. [Open Source]

The Mobius: SourceForge
A few screenshots, details, links.

TriangleOS
32-bit multitasking, multithreaded OS for x86 386+ CPUs, with GUI, FSs, applications, drivers, all in active development. Site has information, news, documents, screenshots, downloadable releases.