ImageOptim decreases the file size of PNG, JPEG, and GIF images, even those "Saved for Web". It combines OptiPNG, PNGCrush, AdvanceComp, PNGOUT, Jpegoptim + Jpegtran, and Gifsicle for the best possible optimization.
Information regarding Project Releases and Project Resources. Note that the information here is a quote from Freecode.com page, and the downloads themselves may not be hosted on OSDN.