ImBatch - ImBatch is a batch image processor with a nice graphical user interface.
TinyPNG - Make your website faster and save bandwidth. TinyPNG optimizes your PNG images by 50-80% while preserving full transparency!
Batch Image Resizer - Resize, crop, shrink, flip, exif-rotate, convert, enhance, process multiple pictures and photos with professional software! 120+ Actions, 30+ Image Formats
ImageOptim - Faster web pages and apps.
Phatch - Phatch = Photo & Batch!
TinyJPG - Compress JPEG images with perfect quality and file size