Google just released new image format for Web, called WebP.
The new WebP format can save 40% smaller from regular JPG format.
It is based on the VP8 image data format with a container based on RIFF.
for more info go to WebP site at http://code.google.com/speed/webp/
directly go to WebP Gallery to see image quality comparison between JPG vs WebP at http://code.google.com/speed/webp/gallery.html