ImBatch - ImBatch is a batch image processor with a nice graphical user interface.
TinyJPG - Compress JPEG images with perfect quality and file size
DVDVideoSoft Image Convert and Resize - Free Image Convert and Resize is a compact yet powerful program for batch mode image processing.
Promo Instant Image Resizer - Automatically optimize images for web & social media (free!)
Batch Image Resizer - Resize, crop, shrink, flip, exif-rotate, convert, enhance, process multiple pictures and photos with professional software! 120+ Actions, 30+ Image Formats
Compressor - Compressor adds power and flexibility to Final Cut Pro X export.