Operating Systems-Programmierung Online
The OSKit Project
An open source set of libraries that can be used as building blocks for an operating system for x86. Includes documentation and publications.
The Operating Systems Resource Center
Extensive information about booting, file systems, memory, architecture, and interfacing with other devices.
Operating System Lecture Notes
Notes on operating system theory, source code of describing actual construction of operating system in C programming language. Also OS construction related links to books, notes, tutorials, and news groups.
The Operating System Developers Homepage
Index of operating systems and links to resources for programmers.