Paint.net
Paint.net is a simple and intuitive free image editor. It has a clean interface with easy to understand features. It also boasts tools and photo effects that are commonplace in paid-for software.
Paint.net also offers the chance of layer creation, which is often found in professional photo editing tools.
Source:
Paint.net
GIMP
GIMP offers a customisable user interface with extensible scripts. With many features to help you to edit your pictures to the maximum, this open source software is better suited to the more experienced user.
Source:
Gimp.org
Picasa
Picasa and Picasa web albums provided by Google offer an easy and convenient way of perfecting photos and online image hosting. The Picasa imaging software offers image recognition, geo-tagging and has RAW format support. Along with integration with the image manager and online photo hosting, Picasa is a favourite photo management tool across all PC operating systems.
Source:
Picasa.google.com
Lightbox Image Editor
Lightbox has a simple interface with a very useful split screen image viewer. The simple correction tools make this software a light digital photo editing tool with the option of upgrading to the pro version.
Source:
Sagelighteditor.com
Autostitch
Autostitch is a free image editor that creates great looking panoramas. Using several pictures, the software is able to compute what the larger panorama should look like and it then outputs one single image.
The easy to use interface means that anyone can use it, regardless of expertise. The desired images are selected and with a click of a button, a realistic and accurate stitched image is produced.
More processing power will be required for higher resolution images and older PCs may take a few minutes to render the final image.
Source:
Cvlab.epfl.ch (brown/autostitch/autostitch)
Photoscape
Photoscape is an image editor and more. It offers everything a desktop photo editing software should deliver and also quirky extras such as a batch editor, GIF animation, RAW converter, face search. It also remains a great picture organiser in the shape of the folder viewer.
Source:
Photoscape.org