Photoscape - high quality photo editing software, that enables you to fix and enhance photos.
ImBatch - ImBatch is a batch image processor with a nice graphical user interface.
Pixelmator - Pixelmator is an image-editing application for Mac and iPad.
DVDVideoSoft Image Convert and Resize - Free Image Convert and Resize is a compact yet powerful program for batch mode image processing.
ACDSee - ACDSee is an image viewer that uses very little system resources, and it has a small, sleek size that won't take up much space on your system.
Ralpha Image Resizer - High-speed image batch conversion tool