ImBatch - ImBatch is a batch image processor with a nice graphical user interface.
ImageOptim - Faster web pages and apps.
Batch Image Resizer - Resize, crop, shrink, flip, exif-rotate, convert, enhance, process multiple pictures and photos with professional software! 120+ Actions, 30+ Image Formats
XnConvert - XnConvert is an easy image converter for graphic files, photos and images available on Windows...
Phatch - Phatch = Photo & Batch!
JPEGmini - JPEGmini - The Photo Optimization Tool Trusted by Tens of Thousands Image Perfectionists