Script-Fu Charcoal v1.0 Tested with Gimp 2.6
A Gimp script which turns a photograph into a black and white image which can look quite like a charcoal drawing. Works with RGB, Indexed and Greyscale images.
Results can be variable and are dictated by the tonal values of the photo used. Although small adjustments can cause quite large differences, the default settings should provide a reasonable starting point but do be prepared to experiment.