For former windows versions there was an application (I don’t remember the name) which was able to keep any window on top of the others. That was pretty helpful while copying text or watching movies during work. For Windows 7 I did not find a free one so I wrote one myself. It is a .NET application so you need the runtime. The application starts as tray icon. When you click it with the right mouse button it shows all processes that have a visible interface. If you click it the window is set on top, if you click it again the window is sent to the background again. The application is not too smart and does not remember the top most windows if you close it. Just set and reset the window again if you accidently closed the application. Hope you like it and consider it as helpful as I do.
You can download it here for free.