ADenyer writes: Want to write your own OS? Fancy trying your hand at x86 assembly language? MikeOS is an open source x86 operating system, designed to show you how a simple OS fits together. Yes, it's 16-bit (for BIOS access), but it's small enough to avoid the old-school DOS memory segment woes, and includes a very thorough HandBook with a guide to writing your first OS kernel. The new 1.1 release includes build scripts for Mac OS X and Windows.