smush.it! : This looks very cool

Firefox Extension. Bulk Uploader. Behind the scenes optimization. Man, this is pretty darn cool!

smush.it!:

"Image optimization is an art that not many people master. There are many good image editing tools that allow us 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."