Information on writing your own operating system, protected mode, and small independent OS projects with freely-available source code. http://my.execpc.com/CE/AC/geezer/os/
A resource center for PC operating system developpers. The aim is to provide reliable documents about software and hardware standards under the aspect of official specifications as well as more friendly documents. http://perso.wanadoo.fr/pierrelib/
An open source operating system for X86 architecture. It also contains documents, specifications explaning various hardware. http://aceos.netfirms.com/