ImageOptim

ImageOptim optimizes images — so they take up less disk space and load faster — by finding best compression parameters and by removing unnecessary comments and color profiles. It handles PNG, JPEG and GIF animations.
ImageOptim seamlessly integrates best optimisation tools: PNGOUT, Zopfli, Pngcrush, AdvPNG, extended OptiPNG, JpegOptim, jpegrescan, jpegtran, and Gifsicle.

It’s excellent for publishing images on the web (easily shrinks images “Saved for Web” in Photoshop) and also useful for making Mac and iPhone/iPad applications smaller (if you configure Xcode).