ToaruOS
Hobby operating system, bootloader, kernel, drivers, C library
..., advanced code editor, and dozens of other utilities and example applications. There are no external runtime dependencies and all required source code, totaling roughly 100k lines of (primarily) C, is included in this repository, save for Kuroko, which lives separately. Through out the project, ToaruOS has also attracted quite a few beginner OS developers who have tried to use it as a reference.