The Guide To Art Schools has published a list of free photo editing software at The 11 Best Free Photo Editing Programs. The list includes:
- Serif PhotoPlus SE
- VC VicMan's Photo Editor
- Ultimate Paint
- Magix Xtreme Photo Designer 6
- Lightbox Image Editor
The Web list includes:
via Keith Cushner.
They left off one of my favorite desktop photo editing tools, Picassa.