A simple script that hides (turns off) all layers in the active document.
Download
To download this script, right-click (Ctrl-click on the Mac) on the link below, and choose "Save Target As".
Hide All Layers
Version: 2.1.0 (July 9, 2009)
Download for:
Photoshop CS2+
Installation
Download the script and copy it into your "Adobe Photoshop CS#/Presets/Scripts" folder.
After restarting Photoshop, the script should appear in the File » Scripts menu.
For more detailed instructions, see the Installing Scripts section of the Scripting Photoshop, Part 1 tutorial.
Tip: Did you know that you can use the command (Ctrl/Cmd+Alt/Opt+Shift+K) to assign keyboard shortcuts to your scripts? You can also record scripts within actions and then assign function keys to the actions.