Windows only: A small background app can give XP and Vista users part of the functionality of "Aero Peek," a smart way of previewing windows and showing the desktop in Windows 7. Unfortunately, that part is just the desktop showing aspect, available from a tray icon installed by the Aero Peek app—though it likely won't be long before we see the windows previews, whether from this developer or elsewhere. In the meantime, it's an intriguingly different way for users of desktop gadgets, or those who have to head back to their desktop often for files, to minimise their active windows. Unlike hitting the Windows Key+D combo, restoring your windows from Aero Peek always keeps whatever windows you had active in the front, and shows what windows you have open in shaded outlines.
Not for everyone, especially those inclined toward keyboard shortcuts, but an intriguing attempt at getting yet another one of Windows 7's features into your Windows desktop. Aero Peek is a free download for Windows systems only.