Today's Google logo is an animation of a dance inspired by the founder of modern dance, Martha Graham. The video below shows how the logo moves:

The animation itself is built using a large CSS3 sprite (which weighs in at 312k). When the page is first loaded, a static image is shown and the css sprite image is loaded in the background. Once the sprite has loaded, then the animation is shown.

The image below shows what the sprite actually looks like:

(click on the image to view full size)