GUIdebook
- Dedicated to preserving and showcasing Graphical User Interfaces. Includes various images, icons, posters, news items and other related materials.
- http://www.guidebookgallery.com/

OldOs.org
- Resource for utilities, history, and much needed to get many old computers up and running, physically or in emulation.
- http://www.oldos.org/

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

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

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

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