GIMP

GIMP kicks butt and takes names, as it scores two-thirds of the total votes this year. Inkscape remains in second place, but it's a very distant second. There certainly are other options available, but time and time again, we turn to GIMP for editing those photos. Although the learning curve for GIMP can be a bit steep, the same often is said for Linux itself. And like Linux, the reward is great.