Smush it – Web Development, Performance and Image Optimization
http://smushit.com/

Image optimization is an art that not many people master. There are many good image editing tools that allow you to get the best visual result for a certain file size but “under the hood” a lot more optimization can be done. Smushit.com is a service that goes beyond the limitations of Photoshop, Fireworks & Co. It uses image format specific non-lossy image optimization tools to squeeze the last bytes out of your images – without changing their look or visual quality. You’ll get a report of how many bytes you can save by optimizing your images and all the changed images as a single zip for download. Smush it comes in different flavors: a) You can upload a bunch of pictures in your browser, b) You can provide them with a list of image urls or c) You can get a Firefox Extension to optimize the images found on any web page. Saving bytes has never been so easy – you point them in the right direction, and they will do the rest for you. A ZIP archive with optimized images will be generated for you. This has been added to World Wide Web Reference Subject Tracer™ Information Blog.