GeekOS is a tiny operating system kernel for x86 PCs. Its goal is to be simple enough for beginners to understand and modify, but realistic enough to be interesting and fun. The primary development environment for GeekOS is Linux or Windows using gcc, nasm, and the Bochs PC emulator.
LKMB is a Perl module that can be used to create a kernel module package, that can later be used to create a package that can be bootstrapped on any GNU machine. It is incomplete, but still partially usable. LKMB is part of the Comprehensive Linux Archive Network (CLAN) meta-project.