I just used this feature for the first time - in MS One Note 2010, click on the "Dock to Desktop" button.
The application then literally docks itself to the bottom of the screen. If a window is maximized above it, that window will not overlap or underlap it - the One Note window has become similar to the task bar in terms of its fixed usage of screen real estate.
Come to think of it, I've seen this one other place: the Windows 7 magnifier.
I'm curious to know how this is pulled off? Is it a window attribute that can be applied in a WinForms app or might I have to use the Windows API/C++ to do it? Or is it even trickier than that?