cyanotype

This script simulates a printing process from 1842:
http://en.wikipedia.org/wiki/Cyanotype
Copy it into the scripts folder from GIMP, you will find it then under Filters -> Artistic -> Cyanotype.

If you like it, hug someone.

An example can be found here:
http://www.flickr.com/photos/28653536@N07/4435497335