A real-time, always on top, “replica” of a window of your choice, based on DWM Thumbnails. Completely written in C# for .NET 4.0/4.5, makes use of the Windows Forms Aero library.
Features
Clone any of your windows and keep it always on top while working with other windows,
Select a subregion of the cloned window:
Store the selected subregions for future use,
Now with relative subregions from the window's borders.
Auto-resizing (fit the original window, half, quarter and fullscreen mode),
Position lock on the screen's corners,
Adjustable opacity,
“Click forwarding” allows to interact with the cloned window,
“Click-through” allows to click through the cloned thumbnail (especially useful with partial opacity),
“Group switch” mode automatically switches through a group of windows while you use them,
Non invasive installation: doesn’t require administrator elevation.
Notes
CodePlex is planning to shut down in December 2017, after that it is unlikely that this package will ever be updated again.