Every Mac user should consider making these applications and utilities part of their standard toolkit
GIMP and Seashore
Like Firefox, much of the value of the GIMP image editor comes from the wide variety of plug-ins built by programmers and artists. Some tagged "script fu" are amalgamations of GIMP operations linked together by the built-in scheme programming language. For basic image tweaking, look to Seashore, a simple version of GIMP with only a few of the most essential routines. It's already a Cocoa app, so there's no need to install X11. For more details on each app, read our full story.