Caesium Image Compressor - Compress your pictures up to 90% without visible quality loss.
Resizing.app - Image resizing has never been so simple with free online resizing.app. Convert, optimize, resize images with ease and for absolutely free.
DVDVideoSoft Image Convert and Resize - Free Image Convert and Resize is a compact yet powerful program for batch mode image processing.
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.
FastStone Photo Resizer - Convert and Rename images in batch mode Support JPEG, BMP, GIF, PNG, TIFF and JPEG2000