If you’re running a website and are trying to minimize the amount of bandwidth being used then one of the things you might be looking at is compressing the images on the site. It may be worth running some of the key images on your site through the Yahoo! Smush.it tool to see what kind of magic it can work on them.
Tools like Yahoo! Smush.it are not trying to compress the images in a way that you start to see artifacts… they will instead optimize them as much as possible without altering their appearance at all. You can bulk upload your images to their servers, and then it will generate a report showing you how much space was saved on each of the images. If you want to grab them all just click on the Download Smushed Images to download them all as a single ZIP file.
The results you’ll get using a tool like Yahoo! Smush.it will probably vary depending on the software you used to originally create the images, but it can’t hurt to see what it can do for you.