Window Detective - Window Detective is a programmer's tool used to "spy" on an application's windows...
Process Explorer - The top window always shows a list of the currently active processes, including the names of their owning accounts, whereas the information displayed in the bottom window depends on the mode that Process Explorer is in: if it is in handle mode you'l…
WinSpy - Retrieve window information.
SystemExplorer - Homepage of System Explorer. Freeware Tool for displaying and managing system internals
Winspector Spy - Have you ever used Spy++ that comes with MSVC?
TaskExplorer - Explore all the tasks (processes) running on your Mac with TaskExplorer.