http://forums.macosxhints.com/showthread.php?t=14110
OnTop is an Application Enhancer which allows you to set windows to always be in the foreground - regardless of what application is currently active (a la many unix and linux window managers). As I find the zoom button mostly useless, I have replaced its functionality with OnTop. Simply press the zoom (+) button (third button on top-left) of any window to lock that window in the foreground. You can then easily switch to other applications while keeping the data you need in view. If you are finished using the window in OnTop mode, simply click the zoom button again to return the window to normal mode.
Red/ hm, några linkar till applikationen tycks vara nere, men den finns ..somewhere! :p
eller: WindowsShade X.> hit CMD 2 times, och det aktiva fönstret är alltid ontop.