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 Sourc...

VISual OPerating SYStem: small, fast, home-brewed, open source OS kernel for x86. Includes project background, screenshots, source code and useful links for OS developers. [Open Source, GPL]

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]

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.

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.

A few screenshots, details, links.

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

Assembly language OS for x86 architecture, hot-swappable kernel, made to serve the Web, written originally for programmer's personal interest and education after moving to the PC platform from his old 8-bit machine. Philosophically similar to V2 OS.

Runs on i386+, 16-bit real mode, FAT12/16/32 (read-only, LFN support), coded in C++; downloads: binaries, source, utilities, game (tetris source); downloads. [Open Source]

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.