I got this from another forum, looks interesting. It's an OS that fits on a floppy.
http://www.menuetos.org/
MenuetOS is a fully 32 bit assembly written graphical operating system. Menuet supports 32 bit x86 assembly programming as a faster and smaller system footprint.
Menuet has no unix roots and the basic system is meant to be a clean asm based structure. Menuet isn't based in any particular operating system, since the idea has been to remove the extra layers between different parts of software, which complicate programming and create bugs.
Menuet's application structure is not specifically reserved for asm programming since the header can be produced with practically any other language. However, the overall application programming design is intended for easy 32 bit asm programming. The GUI is extremely easy to handle with assembly language.
-gosh