"Pie menus are a naturally efficient user-interface technique -- directional selection of pie slice-shaped targets. The cursor starts out in the inactive center region of a pie, and all target slices are large, nearby, and in different directions. Pie menus are quite easy for new users. You simple follow the pop-up directions to use them. They are also extremely efficient for experienced users. Once you know the directions, you can quickly and reliably 'mouse ahead' without looking. Fitts' Law explains the pie menu advantage -- their fast selection speed and low error rate is due to their large target size and the small distance between each item."
Section Topics: The Feng GUI of Pie Menus, Researching and Evaluating Pie Menus, Plugging in Pie Menus, Future Directions, Going to Town with SimCity, Living at Home with The Sims.
I'm in the process of migrating the pie menu stuff from this site and lots of new stuff into the Drupal content management system that I'm using for my blog. As soon as I've moved everything from this site into Drupal, I'll switch this site over to run Drupal, but until then there's still some stuff here that I haven't migrated yet.