If you do a search on Google Images, you'll get a list of thumbnails that point to a frame page: you'll see another small version of the image and the webpage that included the image. But you wanted to see the full-sized image, so you click again. Two clicks instead of one.
If you use Firefox, you can install Customize Google extension that, among other feaures, rewrites links to point straight to the images. Or if you have GreaseMonkey installed, you can add the script from here.
Internet Explorer has a GreaseMonkey clone, called Trixie, that supports most GreaseMonkey scripts, so you can use the script for Firefox.