Ambient Light Falloff, adds the ability to add falloff to the standard ambient light. When run, two new attributes under the light's shape node in the channel box will show up. One controls the light intensity, while the other controls the falloff distance.

This was inspired by the falloff network shown in "Advanced Maya Texturing and Lighting".
Lanier, Lee. Advanced Maya Texturing and Lighting. Indianapolis, Indianna: Wiley, 2006.
ISBN-13: 978-0471794042

Please do not redistribute this script.

Please, enjoy it!

Installation instructions:
Place script into your user scripts directory.
Macintosh: /Users/Shared/Alias/maya/scripts
Windows: C:/Documents and Settings/*User*/My Documents/maya/Scripts

Place ALite_Falloff.xpm into your user icons directory.
Macintosh: /Users/Shared/Alias/maya/icons
Windows: C:/Documents and Settings/*User*/My DocumentsmayaIcons

Usage:
Select a directional light and type ambientLightFalloff(); into your command line, or the script editor and press enter. To create a shelf button type createShelfButton(); .

Legalities:
I take no responsibility for any special, indirect or consequential damages or any damages whatsoever resulting from loss of use, data or profits, whether in an action of contract, negligence or other tortious action, arising out of or in connection with the use or performance of this software.

Thanks:
Henry Korol: Code to add shelf button, from HKMagnetTool

Note:
You can also find my other script to add falloff to a directional light here.