Following tutorial pages for digital photo editing and working on images are available:

1. Correcting slanted horizon lines
Tutorial to correct photos with slanted horizon lines

2. Enhancing dull photos
Tutorial to enhance dull photos

3. Fluttering flag
Tutorial to generate an animated fluttering flag using a Script-fu and the Gimp

4. Watermark it
Tutorial to generate a watermarked image using a Script-fu and the Gimp