Last week I explored, via a post from Julia, a tool which provide an innovative way to navigate through hierarchical menus without using a dropdown menu, nor a tree view, but a pie menu.
I did some search, and I found a complete page on Pie menus written by Don Hopkins, who developed pie menus since 15 years.
Pie menus are used for example in the Sims game, but I also found some nice implementation and demos as ActiveX controls, and Javascript code. It's incredibe the number of languages Don covers, including Forth, Postscript
You have some examples and also an implementation for Mozilla Radial Context.