Squash 2 for Mac - The easiest way to compress and optimize images for the web
ImBatch - ImBatch is a batch image processor with a nice graphical user interface.
Image Resizer for Windows - Lets you resize images by right-clicking.
Batch Image Resizer - Resize, crop, shrink, flip, exif-rotate, convert, enhance, process multiple pictures and photos with professional software! 120+ Actions, 30+ Image Formats
punchi.me - Edit one or several images in a few clics.
DVDVideoSoft Image Convert and Resize - Free Image Convert and Resize is a compact yet powerful program for batch mode image processing.