PicPick is an all-in-one program that provides a full-featured screen capture tool, an intuitive image editor, a color picker, a color palette, a pixel- ruler, a protractor, a crosshair and even a whiteboard.
Seashore is an open source image editor for Mac OS X's Cocoa framework. It features gradients, textures and anti-aliasing for both text and brush strokes. It supports multiple layers and alpha channel editing. It is based around the GIMP's technology and uses the same native file format.
With Picnik you can quickly edit all your online photos from one place. It's the easiest way on the Web to fix underexposed photos, remove red-eye, or apply effects to your photos.