There are probably as many programs that can hide Windows applications as there are reasons you want them hidden. Clicky Gone is a good option - it's light on resources and available as a portable app or with an installer.

As with any good window hiding application, Clicky Gone supports a number of hot keys. By default, they're set to:

• control + alt + left clicking a window's title bar to hide it
• control + alt + enter hides the active window
• control + alt + F12 hides and shows all windows
• control + space displays the Clicky Gone menu at your mouse arrow
• control + alt + return hides everything and can optionally mute your system's sound

In addition, Clicky Gone can add options to hide a window and adjust CPU priority will appear when you right-click its taskbar icon. For the slightly less paranoid, you can also set an option to iconize your windows to the system tray rather than hiding them all inside the Clicky Gone icon.