Easysoft
Operating systems are defined here. All type of operating systems like windows,unix,linux,debian are defined here.open bsd as well as bsd is described here
History of the AmigaOS GUI
Dedicated to the preservation and restoration of the Amiga Workbench's history.
In the Beginning was the Command Line
A history of operating systems, by Neal Stephenson.
OldOs.org
A source for utilities, history, and everything you need to get your old computer up and running, either in emulation or in real life.
Operating Systems History
A Brief History of Computer Operating Systems from the mid 1950s on.
Operating Systems Through Time (8-bits)
A brief history of 8-bit operating systems.