Operating Systems Through Time (8-bits)  
   A brief history of 8-bit operating systems.
   http://www.armory.com/~spectre/tech.html

In the Beginning was the Command Line  
   A history of operating systems, by Neal Stephenson.
   http://www.cryptonomicon.com/beginning.html

History of the AmigaOS GUI  
   Dedicated to the preservation and restoration of the Amiga Workbench's history.
   http://www.gregdonner.org/workbench/

Operating Systems History  
   A Brief History of Computer Operating Systems from the mid 1950s on.
   http://www.cs.gordon.edu/courses/cs322/lectures/history.html

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.
   http://www.oldos.org

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
   http://in.geocities.com/easysoft2002/