This plugin uses channel mixer to increase saturation of the image. Result is Velvia-like image (For those who don't know, Velvia is a slide film from Fuji, and is known for its high saturation). There are implementations of this plugin for The Other Product, and they are often called Digital Velvia or Velvian Colors. For GIMP I couldn't find such a plugin though, so I created my own.
This script requires GIMP 2.0 (1.3 should work too).
The current version is 1.00
Just copy the script to your GIMP scripts directory. Usually this is ~/.gimp-2.0/scripts, but if you want to use the script system-wide then the directory might be something like /usr/share/gimp/2.0/scripts.
Vivid saturation with strength 7
Vivid saturation with strength 12
See other plugins
Author: Olli Salonen