I remember an article in Dr. Dobbs hailing pie menus as the future of user interfaces. It was the early 90's. I have always thought they were a great idea.
Currently Microsoft Office One Note uses them.
Here's a list of references for pie menus (the Dr. Dobbs article is cited):
Every circular menu implementation i've seen still suffers from low command "density", lack of space for text, difficult to use sub-menus, maintaining predictable ordering, and, with touch UIs, commands hidden by the user's own finger.
I really want them, but squares are easier to work with.
One of the selling points has been that they may be used gesturaly, rather than requiring explicit point and click positioning - ie they could be similar to keyboard input in the form of touch typing rather than relying on hand eye coordination.
Dr. Dobbs was wonderful, and I really looked forward to it every month. Ray Valdez wrote a good contract that said I retained the copyright, so I could republish it myself later, which was nice thing for him to do without me even thinking to ask.
And Creative Computing was a great computer magazine, too!
What struck me as I reread the article was that it had been through a rigorous editorial process. No cruft. That clarity is why it stuck with me twenty years on.
It always seemed wrong to throw magazines away, at least so long as they were packed up early as I prepared to move. About 1997 my computer magazines were not. After the books had been boxed, I'd had enough heavy lifting. Now few articles get read twice. Somewhere in a box in Orlando though there may still be a copy of Deskview X.
1993's Secret of Mana was well known for its ring menu. I don't think radial menus are practical with mice, they fit controllers and console games better (where interacting with menus is slower).
Currently Microsoft Office One Note uses them.
Here's a list of references for pie menus (the Dr. Dobbs article is cited):
http://www.cs.cornell.edu/boom/2001sp/bronevetsky/Circle%20M...
In fairness to Dr. Dobbs, they also hailed hypertext as the future about that time, and that one they nailed.