smush it is a service that performs file size reduction for images. If you are already using an expensive program like photoshop, you can already do this. But smush it is free, and it actually reduces file sizes more than what you get out of photoshop without losing any image quality. You can use it by uploading images to their site, point them to URLs no your server. When it's done you get all of the compressed images in a zip file along with a report on the file size savings that you have gotten out of the process.