I have turned on the Opera Turbo option on the Opera web browser to speed up slow wireless Internet connection. Opera Turbo sends the web page to a Opera server which compresses the data before passing it on. So far this has provided 2.2 compression, that is reducing the data received about half the size. This is a worthwhile improvement but not great.
Unfortunately, unlike Opera Mini, the browser for mobile phones, Turbo doesn't reduce the resolution of images, just tries to compress them more efficiently. Images make up a lot of the data in web pages and often the resolution of images is much higher than required (many of the images are window dressing, not providing any useful information and also distracting from the content). It is a shame Opera don't provide an option for reducing the resolution.
One option would be to convert all images to a progressive mode, so the images would appear quickly and then get clearer. This way the web page would appear quickly, if the person really wanted th high resolution images, they need only wait. For cases where you are paying by the Megabyte, you would want to be able to cut off the resolution at a set level.