Anything based on the workstation concepts explored at Xerox PARC, and further pursued at ETHZ, TI and Genera.

Bitsavers has all the necessary papers and manuals, and computer museum as well.

Here are some video sessions.

"Yesterday's Computer of Tomorrow: The Xerox Alto │Smalltalk-76 Demo"

https://www.youtube.com/watch?v=NqKyHEJe9_w

"Alto System Project: Dan Ingalls demonstrates Smalltalk"

https://www.youtube.com/watch?v=uknEhXyZgsg

"Eric Bier Demonstrates Cedar"

https://www.youtube.com/watch?v=z_dt7NG38V4

"The Final Demonstration of the Xerox 'Star' computer"

https://www.youtube.com/watch?v=_OwG_rQ_Hqw

The end of the road from Plan 9, Inferno.

http://www.vitanuova.com/inferno/index.html

http://doc.cat-v.org/inferno/4th_edition/

Small tangent: It's sad that the Mother of All Demos still looks like the future of computing. Google Docs and its siblings come close, but they still don't match it in scope.

Besides what pjmlp said. I was thinking of Plan 9, VMS, NT (the kernel, which takes a lot if ideas from VMS), L4.

Of course, out of these, NT did succeed wildly as well did L4 (e.g. iOS secure enclave).

Some improve in the architecture, some in user land, some in both :).