ImBatch - ImBatch is a batch image processor with a nice graphical user interface.
ImageOptim - Faster web pages and apps.
PNGGauntlet - -Combines PNGOUT, OptiPNG, and DeflOpt to create the smallest PNGs
FILEminimizer Pictures - FILEminimizer Pictures compresses JPEG photos, TIFF, BMP and PNG images and pictures by up to 98%.
Caesium Image Compressor - Compress your pictures up to 90% without visible quality loss.
Shrink O'Matic - Shrink O'Matic is an AIR application to easily (batch) resize (shrink) images.