if you answered Debug View, you get a star, if you don't know about this gem, let me give you a little introduction:
DebugView is an application that lets you monitor debug output on your local system, or any computer on the network that you can reach via TCP/IP. It is capable of displaying both kernel-mode and Win32 debug output, so you don't need a debugger to catch the debug output your applications or device drivers generate, nor do you need to modify your applications or drivers to use non-standard debug output APIs.
DebugView works on Windows 95, 98, Me, 2000, XP, Windows Server 2003, Windows for x64 processors and Windows Vista.
Basically, on your code (pretty much any language that uses the standard windows libraries to output debug), for example C#, you just put something like:
Debug.WriteLine("this is freaking awesome");
you run Debug View, then you run your program (web app or whatever it is you are debugging) and that's it! you get the output in a window much like filemon shows the file activity