GIMP 2

GIMP is an acronym for GNU Image Manipulation Program. It is perfect for such tasks as photo retouching, image composition and image authoring.

It has many capabilities. It can be used as a simple paint program, an expert quality photo retouching program, an online batch processing system, a mass production image renderer, an image format converter, etc.

GIMP is expandable and extensible. It is designed to be augmented with plug-ins and extensions to do just about anything. The advanced scripting interface allows everything from the simplest task to the most complex image manipulation procedures to be easily scripted.

AlbumShaper

Album Shaper strives to be the most friendly, easy to use, open source application for organizing, annotating, framing, enhancing, stylizing, and sharing your digital photos. Album Shaper embraces open formats like XML, JPEG, and XSLT, while supporting Windows, Mac OS X, and Unix users who speak a multitude of languages around the world.

PosteRazor

Poster Creator Print HUGE Posters!
PosteRazor cuts a raster image into pieces which can afterwards be printed out and assembled to a poster.

Panorama Stitch

This is a plug-in for the GNU Image Manipulation Program (GIMP) which stitches together a panorama from digital images. The plug-in is written in Python, and requires that you have a GIMP with python support.