GIMP Plugin Registry

This script adds a realistic film grain effect to a black and white or toned image. To install, copy the attached file to GIMP/share/gimp/2.0/scripts. The larger the file you are running it on, the larger the value you should have for Strength. The value for Sharpness depends on your preferences, but I usually start at 1 and go from there. The lower the value, the sharper the noise.

This is a script which simulates the typical film grain of high ISO pictures. I scripted exactly this description:
http://www.gimpguru.org/Tutorials/FilmGrain/
Copy it into the scripts folder from GIMP, you will find it then under Filters -> Generic -> Film Grain.  read more »