Yahoo! recently launched a tool allowing to compress and optimize the size of any image, on the fly, without losing quality.
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 flavours:
You can upload a bunch of pictures in your browser
You can provide us with a list of image urls or
You can get a Firefox Extension to optimize the images found on any web page
Saving bytes has never been so easy – you point us in the right direction, and we’ll do the rest for you. A ZIP archive with optimized images will be generated for you.