Sample Link: Clouds Full Demo
Debug Sample Link: Clouds in Debug Mode
This one uses 3D CSS transforms to provide an interesting feature for use as a background or in various sites.
In the Clouds Full Demo link moving the cursor in space will change the perspective of the landscape to give the illusion of flying around the skyscape.
The Clouds in Debug Mode link removes the cloud images and replaces them with the css objects they represent so that you can see how the elements work together. There are several layers that move and become visible in this mode.