ImageAlpha - ImageAlpha is a GUI for pngnq and pngquant.
ImageOptim - Faster web pages and apps.
PNGGauntlet - -Combines PNGOUT, OptiPNG, and DeflOpt to create the smallest PNGs
Optimage - Advanced image optimization tool
Tinybeest - A Mac app and Chrome extension that optimizes/compresses images and PDFs.
XnConvert - XnConvert is an easy image converter for graphic files, photos and images available on Windows...