The following items are some links to articles and videos about pie menus and user interface design that Don Hopkins shared and discussed with Krystian Samp in their correspondences over the years about his research and thesis about The Design and Evaluation of Graphical Radial Menus.
A paper by Jack Callahan, Don Hopkins, Mark Weiser and Ben Shneiderman, presented at ACM CHI'88 Conference, Washington DC, 1988, describing a controlled study comparing pie menus and linear menus.
http://www.donhopkins.com/drupal/node/100Early design notes about pie menus, by Don Hopkins.
http://www.donhopkins.com/drupal/node/82A paper by Ben Shneiderman, Catherine Plaisant, Rodrigo Botafogo, Don Hopkins, William Weiland, describing the HyperTIES hypermedia browser on the Sun workstation, which uss pie menus.
http://www.donhopkins.com/drupal/node/102A paper by Don Hopkins, describing the PostScript Interactive Bug Eradication Routines, a visual user interface to the graphical PostScript programming environment in the NeWS window system, which uses pie menus. Presented at the Usenix Monterey Graphics Workshop.
An article by Don Hopkins about pie menus, published in the December 1991 issue of Dr. Dobb's Journal, as the lead article of the user interface issue.
http://www.donhopkins.com/drupal/node/98An illustrated description of free open source pie menus implemented in Python for the GTK user interface toolkit using the Cairo graphics library, running in the OLPC Sugar environment, showing various item layout techniques, including hybrid linear menus and rings.
http://www.donhopkins.com/drupal/node/128
A video with an excerpt from "All The Widgets" CHI'90 Special Isssue #57 ACM SIGGRAPH Video Review, showing various kinds of pie menus implemented by Don Hopkins on the NeWS window system. Research performed under the direction of Mark Weiser and Ben Shneiderman.
http://www.donhopkins.com/home/movies/JustThePieMenus.movA video of a talk by Ben Shneiderman and demos of pie menus developed at the University of Maryland Human Computer Interaction Lab by Don Hopkins.
http://www.donhopkins.com/home/movies/HCILPieMenus.movA video demo of a free open source window manager with pie menus developed for the X10 window system by Don Hopkins.
http://www.donhopkins.com/home/movies/X10PieMenuWM.movA video of the pie menu experiment performed for the paper "An Empirical Comparison of Pie vs. Linear Menus", running on the X10 window system.
http://www.donhopkins.com/home/movies/PieMenuExperiment.movA video demo of free open source precision pie menus running on the NeWS window system, by Don Hopkins.
http://www.donhopkins.com/home/movies/PrecisionPieDemo.movA video demos of pie menus in UniPress Emacs running on the NeWS window system, developed by Don Hopkins.
http://www.donhopkins.com/home/movies/NeMACSDemo.movA video demo of pie menus in the PSIBER Space Deck, free open source software running on the NeWS window system, by Don Hopkins. Described in the paper "The Shape of PSIBER Space"
http://www.donhopkins.com/home/movies/PSIBERDemo.movA video demo of free open source pie menus and tabbed window management in The NeWS Toolkit, developed in 1990 by Don Hopkins.
http://www.donhopkins.com/home/movies/TabWindowDemo.movA video of a talk about pie menus and self revealing gestural user interfaces given by Don Hopkins, and a talk given by Don Norman, at the IBM Almaden New Paradigms for Using Computers Workshop, with an introduction by Ted Selker.
http://www.donhopkins.com/home/movies/NPUCHopkinsNorman.movA video demo of free open source ActiveX pie menus for Internet Explorer, by Don Hopkins.
http://www.donhopkins.com/home/movies/ActiveXPieMenus.movA video demo of pie menus for SimCity running on X11, by Don Hopkins.
http://www.donhopkins.com/home/movies/X11SimCityDemo.movA video demo of pie menus in The Sims, by Don Hopkins.
http://www.donhopkins.com/home/movies/TheSimsPieMenus.movA video demo of free open source 3D pie menus in Unity3D, by Don Hopkins.
http://www.youtube.com/watch?v=sMN1LQ7qx9gA video demo of iLoci, a reformulation of user editable pie menus as a network map of rooms with two-way links supporting gestural navigation, instead of a heirarchy of menus and sub-menus.
http://www.tiburon-tv.com/2008/12/09/iphone-app-iloci-by-don-hopkins-mobile-dev-camp/A video demo of a MediaGraph user interface prototype developed by Don Hopkins for Will Wright's Stupid Fun Club, featuring the Unity3D pie menus and a user editable gesture navigable graph similar to iLoci.
http://www.donhopkins.com/home/StupidFunClub/MediaGraphDemo1.mov