You know now that Page Speed can automatically optimize your images. Another way to do this is with Yahoo’s Smush It, which is a set of image optimization tools that analyze your images, create the smallest possible versions and sends you a ZIP file of them all.
You can use Smush.it directly in the browser or automatically from YSlow. The website tells you how many bytes you can save by optimizing your images. This is yet another cool thing to show potential clients when pitching for a job.